Your Nightmare

If you find something and it's NOT yours, return it. At most, leave it alone. Once you take possession of it, and then hold onto it or use it, you are now a thief. This is especially true when you know how to contact the owner.

Furthermore, if you know someone that has done this you can be criminally charged as an accomplice. You should morally do the right thing anyway. What if YOUR item went missing?