What would you have done?

I'd have returned it, too. I don't really care much for money itself, and it's certainly not worth getting the poor teller fired or getting her pay reduced over it. Everybody makes mistakes sometimes. I know how hard a job is to come by lately, I would hate to feel responsible (even partially) for someone losing theirs atm. :\

Other than that.. I dunno, it's just not in my character to keep what isn't mine. I guess I think of it as a test of my character when something like that happens. You know, what you do when no one's looking.