Oh man.. I would be steaming mad first off. I would have to calm myself down (and that is not even mentioning the rage my hubby would feel!) before confronting the person who did it..
Reminds me.. oddly enough of an ATV story! Mark's cousins and friends came out, and he let them go for a spin on our Polaris. So.. a few days go by. I pull it out of the barn to wash it.. one headlight is GONE. I about flipped, called my hubby and he flipped. Calmed down.. talked to his cuz who had not even ridden it (he has his own that he prefers.) He brought the guys out, so he did the noble thing and paid for the parts to fix it.
Were there any people who were guests of people that you're close to? If so, I would confront your closer friends first. Maybe something happened to them as well that they are iffy about (like, thinking that they're missing something..) and your accusations would tip them over the edge. At any rate, that's no chump change you're missing, and someone should answer for it.
Unless maybe you actually did lose the $. I lost $40 at the mall once. I know that no one touched my purse b/c it never left my shoulder. Went for my money.. gone!