YSK: If you find a missing wallet and want to be a REALLY good person, check the bank of their credit/debit card and drop it off there.
Why YSK: This is the way to pretty much guarantee it gets back to them. The bank has their contact info, will get in touch with them, and keep it safe in the vault until they come to pick it up.
This happened to me last week, I got a call just a few hours later, and got it back the next day. All the money was gone, presumably thanks to the less-good person before them, but my main dread was getting all the various cards replaced which were all still there. I literally cried with relief. I hope to be able to pay it forward some day. #education source