I agree that if you can confidently decide whether 1) or 2) is the case, the actions you laid out are the correct ones. things are rarely so clear cut in my ex

I agree that if you can confidently decide whether 1) or 2) is the case, the actions you laid out are the correct ones. things are rarely so clear cut in my experience, especially when you only have the resources of a sole private citizen at your disposal. my "contrived example" is actually lifted from a similar experience I had in college. I found it pretty suspicious at the time, because the gatherings where the other people lost their wallets were quite small. ultimately, I acknowledged privately that I could not conclude one way or the other, so publicly I defended my friend. at the same time, I was always a bit more careful of my stuff when we were hanging out (no idea whether they noticed this). my point is that there is a difference between taking punitive action against a person and taking protective actions towards oneself. my position is that there is no inherent contradiction in being too uncertain to punish but certain enough to protect yourself, provided that it does not unduly harm the other person.