I asked my wife about a several weeks later if she would tell me if she was ever unfaithful and she said no
You say you felt her answer was a bit strange. To me, it seems you might have asked an odd question that she wasn't expecting and hadn't thought about. The 'no' might have been to the question she perceived, vis-a-vis, would you ever be unfaithful, which she then clarified afterwards.
Alternatively, I recall reading an article years ago, that suggested if you had cheated once and had realised afterwards that you had made a terrible mistake, that you shouldn't tell your partner if all you wanted to do was get the guilt off your own back. Better, it suggested, that you live with the pain of your guilt than that you put your partner through the pain of knowing, assuming you want to continue in your relationship. I can see sense in that somewhere. So if you asked me that question, I might well reply no, however it could only ever be theoretical, because I am as sure as I can be that I would never cheat.
But... really, was it a full unopened box that had never been opened? Otherwise, were you monitoring the contents? Because there are long disused condoms in my bedside cabinet. Pretty sure neither me, nor DH would have any idea how many are left. Have you left them there as a test? Is the fact that your wife might get annoyed because you have form for thinking the worst? Or is this the first time it's crossed your mind?