I would hunt the guy down ASAP..and send his wallet back with the money credit cards etc (well if he had some nudies of his girlfriend..those might be missing) and I would refuse any type of reward....to all you fucks that would keep the money a big FUCK YOU... You are the type of people that make our society shit.....
Send it back bro. Karma is a bitch. Think of how good you would feel if somebody did that for you. People have done it for me and it felt great. you will respect yourself.