Wow, Im really late on this thread huh.. I hope glo hasn't spent the money yet lol
I just wanted to give my input... According to Islam, if you see something you shouldn't pick it up... and if you do pick it up... you cannot make public announcement.. "I FOUND A ROLEX, are any of you owners of this watch"? lol what do you think is gonna happen? People gonna say YES!! lol Im the owner.... So basically, you don't pick it up... owner will eventually find it... if you do pick it up... you hold it for a year if no one comes forward.. its yours.
Now in the case of money... its impossible to find the owner of the bill... So, the best thing to do is not to pick it up... and if you have picked it up.. you should give it to charity.
Because it's not your money, and if you give it to charity... you've just helped feed 10 children in Africa

(maybe more)
So both, you and the person should get the reward!
ok, peace!