Cesar Moya was convicted in the United States District Court for the Northern Dis*1046trict of Illinois for possession of cocaine with intent to distribute in violation of 21 U.S.C. § 841(a)(1). United States v. Moya, 561 F.Supp. 1 (N.D.Ill.1981), aff'd, 704 F.2d 337 (7th Cir.), vacated and remanded, — U.S. —, 104 S.Ct. 418, 78 L.Ed.2d 355 (1983). On appeal, a majority of this court held that the three hour detention of Moya’s luggage based upon the law enforcement agents’ reasonable suspicion that the bag contained contraband did not violate the fourth amendment prohibition against unreasonable searches and seizures. United States v. Moya, 704 F.2d 337 (7th Cir.), vacated and remanded, — U.S. —, 104 S.Ct. 418, 78 L.Ed.2d 355 (1983). The Supreme Court vacated and remanded the decision for further consideration in light of United States v. Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983). In Place, the Court held that a ninety minute detention of luggage while awaiting the arrival of a trained narcotics detecting dog based upon less than probable cause violated the fourth amendment. Id. 103 S.Ct. at 2645-46.
This court then sought additional briefing from the parties on the following points:
(1) Whether there was probable cause for the seizure of Moya’s shoulder bag?
(2) Whether there was any legal justification for the warrantless seizure of the clear plastic bag from Moya’s shoulder bag, in particular whether the plastic bag fit within the “plain view” exception to the warrant clause?
(3) Whether the three hour detention of Moya’s shoulder bag could be persuasively distinguished from the ninety minute detention that occurred in Place?
We now hold that the government waived the issue of probable cause by failing to raise it either at trial or on appeal, and that, in any event, the prolonged detention of Moya’s shoulder bag violated the fourth amendment.
I
The rule is well established that an appellate court will not review an issue raised for the first time on appeal unless the trial court has committed plain error. See United States v. Spears, 671 F.2d 991, 992 (7th Cir.1981); Fed.R.Crim.P. 52(b). In Steagald v. United States, 451 U.S. 204, 101 S.Ct. 1642, 68 L.Ed.2d 38 (1981), the Supreme Court addressed the issue of waiver where, as here, the government failed to raise an alternative ground for the admission of evidence and the ground on which the lower court admitted the evidence was later rejected. The Court held that the government waived the alternative ground: “The Government ... may lose its right to raise factual issues ... when it made contrary assertions in the courts below, when it has acquiesced in contrary findings by those courts, or when it has failed to raise such questions in a timely fashion during the litigation.” Id. at 209, 101 S.Ct. at 1646; cf. United States v. Duckworth, 699 F.2d 424, 425 (7th Cir. 1983) (raising of issue by government for first time on petition for rehearing deprived defendant of right to fully and fairly litigate the claim). The Court rejected the government’s assertion that the alternative ground for admitting the evidence had become viable only after a Supreme Court decision issued posttrial which changed fourth amendment law. The Court found that the government could and should have anticipated the change. Steagald v. United States, supra, 451 U.S. at 210 n. 5, 101 S.Ct. at 1647 n. 5; cf. Reed v. Ross, — U.S.—,—-—, 104 S.Ct. 2901, 2908-10, 82 L.Ed.2d 1 (1984) (habeas petitioner establishes cause for failure to raise constitutional claim in state court only where “claim is so novel that its legal basis is not reasonably available to counsel”).
At least one circuit court used a similar analysis and refused to review a probable cause claim raised by the government on remand from the Supreme Court. United States v. West, 723 F.2d 1 (1st Cir.1983). In West, the government conceded at trial that there was no probable cause and argued only that the officers had reasonable suspicion to detain the defendant’s luggage. The district court found that the detention of the luggage, while awaiting *1047examination by a narcotics detecting dog was proper; the First Circuit affirmed. United States v. West, 651 F.2d 71 (1st Cir.), vacated and remanded, — U.S. —, 103 S.Ct. 3528, 77 L.Ed.2d 1382 (1983). On remand for reconsideration in light of Place, supra, the court held: “Given this concession by the government at trial, the issue of probable cause cannot be resurrected on appeal____ Although we might consider the argument were it ‘so compelling as virtually to insure the government’s success’ ... this is scarcely such a case.” United States v. West, supra, 723 F.2d at 2 n. 1 (citations omitted).
In the instant case, the government not only failed to raise the issue of probable cause, but effectively conceded that no probable cause existed. In a motion to suppress the contents of his shoulder bag, Moya argued that the bag was seized without probable cause, thus tainting the later-obtained search warrant and ultimate search of the bag. Defendant’s Motion to Suppress at 3, United States v. Moya, supra, 561 F.Supp. 1. The government responded that only “reasonable suspicion” was required to justify the detention of Moya’s bag. Government’s Response to Defendant’s Motion to Suppress at 5, United States v. Moya, supra, 561 F.Supp. 1. At no time did the government argue that the officers had probable cause to detain the bag, see id., and the government expressly conceded that the seizure of the clear plastic bag was unlawful, id. at 4 n. 2, 6. On appeal to this court, Moya again argued that the officers needed probable cause to justify the detention of his shoulder bag. Brief of Defendant/Appellant at 7, 9-20, United States v. Moya, supra, 704 F.2d 337. The government again argued only that the officers had reasonable suspicion to detain the bag. Brief for the United States, United States v. Moya, supra, 704 F.2d 337. The government acknowledged the Second Circuit’s opinion in United States v. Place, supra, 660 F.2d 44 (2d Cir.1981), affd, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983), which held that probable cause is required to detain luggage for a prolonged period of time. The government responded that Place was not the law of this circuit. Brief for the United States, supra, at 19 n. 15. The government again conceded the illegality of the seizure of the clear plastic bag. See id. at 21 n. 16.
The Supreme Court’s decision in United States v. Place, supra, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110, did not work a dramatic change in the law. Litigation of the issue of detaining luggage while waiting the arrival of a trained narcotics detecting dog was of recent vintage when the government presented its arguments in the district court. The circuits split on the issue. Compare United States v. Klein, 626 F.2d 22, 26 (7th Cir.1980) (first applying reasonable suspicion standard to detention of luggage) with United States v. Place, supra, 660 F.2d at 50-52 (requiring probable cause for a prolonged detention of luggage). The Supreme Court had not yet addressed the issue. When the Court did address the issue in United States v. Place, supra, 103 S.Ct. at 2645-46, the Court’s holding was based on long-established fourth amendment principles. We conclude that under these circumstances the government should reasonably have anticipated the Court’s decision. Cf. United States v. Johnson, 457 U.S. 537, 551, 102 S.Ct. 2579, 2588, 73 L.Ed.2d 202 (1982) (“the Court has not ... read a decision to work ‘a sharp break in the web of the law,’ ... unless that ruling ... explicitly overrules a past precedent of this Court, ... or disapproves a practice this Court arguably has sanctioned in prior cases, ... or overturns a longstanding and widespread practice to which this Court has not spoken, but which a near-unanimous body of lower court authority has expressly approved.”); Steag-ald v. United States, supra, 451 U.S. at 210 n. 5, 101 S.Ct. at 1647 n. 5 (government should have raised issue in trial court where subsequent Supreme Court decision “altered Fourth Amendment jurisprudence to some extent, [but] the rationale of that decision was in large part simply an extension of this Court's earlier reasoning”).
*1048The district court, of course, was not asked by the government to make a specific finding of probable cause. As a result, there is no “finding” for us to review. The government has not offered any persuasive reason for its failure to raise the issue of probable cause until this late stage in the proceedings. If the existence of probable cause was as apparent as the government now contends, we fail to see why the government failed to raise the issue before the district court. We now hold that the government waived its claims that the officers had probable cause and that the seizure of the clear plastic bag fits within the “plain view” exception to the warrant requirement. See also United States v. West, supra, 723 F.2d at 2 n. 1; cf. United States v. Hoffman, 607 F.2d 280, 285-86 (9th Cir.1979) (refusing to consider whether “inevitable discovery” doctrine justified warrantless seizure where issue was not raised in the district court).
II
Even if the government had not waived its probable cause claim, we do not believe that the evidence seized from Moya’s shoulder bag was admissible. After examining the merits of the government’s claim, we conclude that no probable cause existed prior to the positive reaction to Moya’s shoulder bag by the narcotics detecting dog.1
A
The implications for personal privacy resulting from a finding of probable cause require that the standard be rigorously enforced. Probable cause requires sufficient evidence to lead a reasonable and prudent person to believe, not merely suspect, that a crime has been or is being committed. Brinegar v. United States, 338 U.S. 160, 175-76, 69 S.Ct. 1302, 1310-11, 93 L.Ed. 1879 (1949). We must be especially cautious when the evidence that is alleged to establish probable cause is entirely consistent with innocent behavior. See Reid v. Georgia, 448 U.S. 438, 441, 100 S.Ct. 2752, 2754, 65 L.Ed.2d 890 (1980) (per curiam); United States v. Saperstein, supra, 723 F.2d at 1229. We find that the evidence available to the officers in this case was insufficient to lead a reasonable person to believe that a crime was being committed.
It is clear that the officers did not have probable cause at the time that they approached Moya in the taxicab line outside the airport. At that time the officers knew that Moya was arriving from Miami, had only carry-on luggage, scanned the crowd repeatedly, looked back over his shoulder, and “sought the privacy of a washroom stall for some reason other than a desire to relieve himself.” United States v. Moya, supra, 561 F.Supp. at 4. Indeed, this information was insufficient to establish even reasonable grounds for suspecting that Moya was carrying contraband. Id.; see Reid v. Georgia, supra, 448 U.S. at 441, 100 S.Ct. at 2754 (reasonable suspicion not established by observations that suspects deplaned from a principal place of origin of cocaine for distribution, arrived in the early morning when law enforcement activity is diminished, carried only shoulder bags, and attempted to conceal that they were traveling together).
After being approached in the taxicab line, four events occurred which the district court found sufficient to give rise to reasonable suspicion. First, when asked for identification Moya responded that he had none. Then, when asked again for identification once inside the terminal, Moya proceeded to produce a driver’s license from his shoulder bag. Third, while reaching into the bag, Moya exposed the corner of a clear plastic bag. Finally, when asked to produce the plastic bag, Moya responded that no plastic bag existed. See United States v. Moya, supra, 561 F.Supp. at 8. These four events were not sufficient to give rise to probable cause.
*1049Probable cause is not established either by failing to present identification upon request by a law enforcement officer, see Brown v. Texas, 443 U.S. 47, 52, 99 S.Ct. 2637, 2641, 61 L.Ed.2d 357 (1979); United States v. Brown, 731 F.2d 1491, 1494 (11th Cir.1984), or by carrying a plastic bag in one’s travel luggage, see infra at 1050. The only question presented by the instant case is whether Moya’s false responses to the officers concerning identification and the plastic bag gave the officers probable cause to believe he was engaged in criminal activity. There are several innocent explanations for a lack of forthrightness with law enforcement officers. A person could simply be mistaken or have forgotten; this explanation appears particularly plausible if one considers the stress that someone might reasonably feel when subjected to police questioning. Alternatively, a person could be attempting to conceal information that is personal or embarrassing but not criminal, or supplying answers that she or he believes will expedite the questioning process.2 We conclude that Moya’s seeming dishonesty with the officers was insufficient to establish probable cause. See also United States v. Place, supra, 103 S.Ct. at 2640, 2644 (no probable cause found although the defendant falsely reported to law enforcement officers that his luggage had already been searched by other officers).
B
The district court found that the warrantless seizure of the plastic bag containing drug paraphernalia was unconstitutional and excluded the evidence from consideration in determining the reasonableness of the detention of the shoulder bag. See United States v. Moya, supra, 561 F.Supp. at 8-9. We agree with the district court (and the government’s position at trial) that the search was illegal and the contents must therefore be excluded from our probable cause determination.
The district court correctly concluded that the plain view exception to the warrant clause was inapplicable to the seizure of the plastic bag, see United States v. Moya, supra, 561 F.Supp. at 9 n. 6. The plain view doctrine authorizes the warrant-less seizure of personal property where the initial intrusion which affords the officers a plain view is lawful, the discovery of the property is inadvertent, and the incriminating nature of the property is “immediately apparent.” Coolidge v. New Hampshire, 403 U.S. 443, 466, 91 S.Ct. 2022, 2038, 29 L.Ed.2d 564 (1971) (plurality opinion); United States v. McDonald, 723 F.2d 1288, 1295 (7th Cir.1983). The phrase “immediately apparent” does not “imply that an unduly high degree of certainty as to the incriminatory character of evidence is necessary for an application of the ‘plain view’ doctrine.” Texas v. Brown, 460 U.S. 730, 103 S.Ct. 1535, 1542, 75 L.Ed.2d 502 (1983). ■The character of the property must be such as to give the officers “probable cause to associate the property with criminal activity.” Payton v. New York, 445 U.S. 573, 587, 100 S.Ct. 1371, 1380, 63 L.Ed.2d 639 (1980); see Texas v. Brown, supra, 103 S.Ct. at 1542.
There is nothing apparently incriminating about a plastic bag. Plastic bags are used by travelers for a variety of innocent purposes. Bags are used, for example, to carry wet items, to contain items that may spill, and to keep items sanitary. The exposure of the corner of the clear plastic bag did not give the officers probable cause to believe that the plastic bag contained contraband. Contrast Texas v. Brown, supra, 103 S.Ct. at 1543 (the incriminating nature of a tied-off balloon “common[lyj” used to carry narcotics found sufficiently apparent); id. at 1545 (Powell, J., concurring) (“We are not ad*1050vised of any innocent item that is commonly carried in uninflated, tied-off balloons such as the one ... seized.”).
The district court’s conclusion that the plain view exception is inapplicable to the seizure of the contents of Moya’s plastic bag is further supported by consideration of the principle underlying the exception. “The principle is grounded on the recognition that when a police officer has observed an object in ‘plain view,’ ” the owner has no remaining privacy interest in the object. Texas v. Brown, supra, 103 S.Ct. at 1541. It is clear that Moya retained an expectation of privacy in the contents of his plastic bag even after exposing a corner of the bag.
Ill
In United States v. Place, supra, the Supreme Court found unreasonable the ninety minute seizure of the defendant’s luggage based only on the law enforcement officers’ reasonable suspicion that the luggage contained contraband. The Court stated, “[W]e have never approved a seizure of the person for the prolonged 90-minute period involved here and cannot do so on the facts presented by this case.” 103 S.Ct. at 2646. The Court, however, “declinefd] to adopt any outside time limitation” beyond which all such seizures would be unreasonable, and left the question of the reasonableness of a detention for resolution on a case-by-case basis. Id. We find no persuasive grounds for distinguishing the three hour seizure of Moya’s shoulder bag from the ninety minute seizure disapproved in Place.
The officers who apprehended Moya admitted that they stationed themselves at the airport specifically to investigate the transportation of illicit drugs. Under these circumstances, we believe it is reasonable to expect officers to arrange to have a narcotics detecting dog readily available. See also United States v. Puglisi, 723 F.2d 779, 791 (11th Cir.1984) (three hour detention of luggage while awaiting canine sniff-test unreasonable where officer had alternatives of having trained dog at airport or directing agents in the destination terminal to conduct the search); cf. United States v. West, supra, 723 F.2d at 3 (remanding to district court question why agents did not have trained dog in immediate vicinity); United States v. Sanders, 719 F.2d 882, 887 (6th Cir.1983) (detention found unreasonable where no explanation why agents did not arrange to conduct investigation at airport). In fact, the record in the instant case indicates that Moya’s shoulder bag was eventually tested by a dog from the United States Customs Department located in the airport’s international terminal; there is no explanation why it took three hours to transport the luggage from one terminal to another. See Transcript of December 1, 1980, at 32-33.
In addition, the Court in Place found the unreasonableness of the search exacerbated by the officers’ failure to inform the defendant where his luggage was being detained or how long the detention would last, and to make arrangements for the return of the luggage if the sniff-test was negative. 103 S.Ct. at 2646. See also United States v. Saperstein, supra, 723 F.2d at 1233 n. 18. The officers acted similarly unreasonably with respect to the seizure of Moya’s luggage.
We recognize that in Place the New York law enforcement officers were given advance notice by agents in Miami that the defendant, a suspected drug courier, was going to be arriving. The Supreme Court held that the diligence with which law enforcement officers pursue an investigation is one factor, although not the only factor, to be considered in assessing the reasonableness of a detention. The Court concluded that the officers involved in Place were less than diligent because they could have, but failed to “arrange for their additional investigation ..., thereby ... minimizing] the intrusion on respondent’s Fourth Amendment interests.” United States v. Place, supra, 103 S.Ct. at 2645-46. Because the officers had alternatives that would have minimized the intrusion on Moya’s fourth amendment interests, we are not persuaded by the argument that the *1051officers had no advance warning that Moya would be arriving at the airport.
The judgment of the district court is vacated and remanded with instructions to suppress all evidence seized from Moya’s shoulder bag.
. Even if the officers had probable cause to believe Moya’s bag contained contraband, there would be a question whether the three hour detention of the bag before seeking a search warrant was reasonable. See United States v. Saperstein, 723 F.2d 1221, 1232 (6th Cir.1983).
. We do not condone dishonesty with police officers. We note, however, that people are entitled to refuse to provide information to the police. See U.S. Const, amend. V; United States v. Mendenhall, 446 U.S. 544, 554, 100 S.Ct. 1870, 1877, 64 L.Ed.2d 497 (1980) (plurality opinion) (rationale for permitting investigative stops is that answers are consensual); Miranda v. Arizona, 384 U.S. 436, 458-65, 86 S.Ct. 1602, 1619-23, 16 L.Ed.2d 694 (1966). Nevertheless, many people may have difficulty forthrightly refusing to give police officers requested information.