I realize it is not the same as finding a friend, but I recently found five crisp $20 bills in a used logic text book at an Amvets thrift store. I opened the book because it was written by Irving Copi, who wrote my undergrad logic text. I was paranoid it was counterfeit, but it was very much real money. To make things better, the first $20 I spent was to get a pizza and the employee said a mistake happened at the pizzeria and they accidentally made too many pies and gave me an extra large pie for free. I was on a roll.