one time when I worked at a lumber yeard, I was pushing in carts back into the store and I found two 20's on the ground. I picked them up and put them in pmy pocket and then looked around. I found 2 more. hot damn.
then I followed where they seemed to have come from (they were forming sort of a wind blown trail) and there was a guy there trying to put a 4x8 sheet of 3/4inch plywood into his car by himself. 20's were spilling out of his pocket and there were another 3 or so on the ground there by him.
I picked up the 20's off the ground and then pulled out the 20's I had found and gave them to him and mentioned that they must have fallen out while he was struggling with that wood and then did he want some help loading that shit?
he took the money as if I had given him 2 pennies and then said he didn't need help with the wood.
oh well - I tried to do a good deed and vaguely felt good for it.
all I know is that if I lost my wallet, I'd want the person to send it back - I'd care less about the cash in it, but I'd love it if the cash were there. reward or not, it is the right thing to do to send it back to them.
if their driver's license is in there, then you should have their address - or you can call the credit card companies and let them know you found it and they will put you in touch with the person.