man returns a strangers wallet and is rewarded...would you reward?

[tdarko]

yesterday i was at the mall doing some christmas shopping, at around lunchtime i went to the corner bakery to eat some soup and since i was by myself i decided to sit out on their patio area to people watch (i sometimes like to do this).

half-way through my soup i notice one man (well dressed) walking toward the corner bakery and another man running up behind him. the man behind him says, "you dropped your wallet back there (pointing behind him)." the man with the wallet gives a look of total relief and says, "oh my, thank you so so much. here..."

then he rummages through his wallet and since this is happening right in front of me i can see that he has quite a bit of money in that wallet...my guess is probably a grand in $100's and a couple hundred in $20's (i guess he christmas shops w/ cash?).

anyway he takes out a $20 and hands it to the guy and tells him "thank you for returning the wallet." the guy looks at him strangely and declines, he insists on giving the money again and after a back and forth match the money is finally accepted.

my question to OOT: if you had this amount of money in your wallet and you drop it and a stranger returns it, do you give him any money? if so, how much? explain why you would or wouldn't give him any money.