We are married, not room mates, she goes in my wallet, goes on my computer, uses my phone, to me not nosey in marriage.
Been married happily 25+ years here.
If you had found them, walked in the house, said "Hey honey I found these in the garage. Are you having a problem?" I'd have been fine with it. When you checked how many were missing etc? That is going too far and into you want a reason to be mad about it. For me thats a fight waiting to happen as it would feel more like a dad checking up on me than a concerned hubby.
Remember she felt she had to hide it. Shes uptight on the issue to begin with. Adding any fuel to the fire? Not good in my opinion.
The best answer might be to ask if they could possibly be the kids. Gives her a safe way to fess up.