(specially concurring).
I concur in the result reached by Judge Sutin; I do not join in the opinion. My special concurrence is on the following basis.
1. Exhibit 2, the asserted contract for the 1965 truck, has not been included in the appellate record, however, there is testimony about the exhibit. There were two witnesses — one of the plaintiffs and defendant. Plaintiff’s testimony is substantial evidence supporting the findings of the trial court that go to the dealing by the parties concerning the 1965 truck.
Because Exhibit 2 was not signed, and the testimony about the exhibit did not establish that delivery of the 1965 truck to the plaintiffs amounted to an acceptance by defendant of the plaintiffs’ offer to buy, defendant recognizes that evidence as to the parties’ language and conduct, the objective of the parties and the circumstances of the dealing between the parties must be considered. Shaeffer v. Kelton, 95 N.M. 182, 619 P.2d 1226 (1980).
Defendant states that the plaintiffs’ offer to buy was accepted by defendant’s performance. See Keeth Gas Co., Inc. v. Jackson Creek Cattle Co., 91 N.M. 87, 570 P.2d 918 (1977). The question of performance was a disputed issue of fact; the testimony as to the circumstances of the dealing between the parties was such that the trial court could properly find as it did.
In essence, defendant argues that its evidence should have been accepted by the trial court as true, and the evidence of the plaintiffs should have been rejected. Credibility of the witnesses was- for the trial court. Lujan v. Pendaries Properties, Inc., 96 N.M. 771, 635 P.2d 580 (1981).
2. Defendant claims that the judgment in the prior replevin action barred the plaintiffs’ suit for conversion or unjust enrichment under the doctrine of res judicata. This was an affirmative defense which the defendant had the burden of proving. Rule of Civ.Proc. 8(c). The record on appeal, see R.Civ.App. 7, does not show that the judgment in the replevin action was introduced into evidence. Assuming that judgment was before the trial court by virtue of the summary judgment proceeding which occurred prior to trial, that judgment recites only that “plaintiffs did not meet their burden of proof on the theory of replevin”. There was nothing showing a judgment on the merits in the replevin action. See Trujillo v. Acequia de Chamisal, 79 N.M. 39, 439 P.2d 557 (Ct.App.1968) and § 42-9-14, N.M. S.A.1978. I agree with defendant that evidence is lacking to support Findings Nos. 11 and 12, nevertheless, the trial court correctly rejected the defense of res judicata because of failure of proof.
3. Defendant seeks reversal of the trial court’s judgment only on the grounds discussed under Points 1 and 2. As Judge Sutin points out,- defendant does not challenge the conclusion that defendant was unjustly enriched. The discussion of the substantive law of unjust enrichment is inappropriate in light of the grounds relied on by defendant for reversal. See State of New Mexico ex rel. Human Services Department v. Staples, 98 N.M. 540, 650 P.2d 824.