I too found a wallet many years ago when I worked at a supermarket, in my mid-twenties. It had a few hundred dollars in it, along with the person's electric bill ( I suspected that was the reason for the cash), and they had mistakenly left it at the register where I worked. Being an American, my understanding of our culture is that it is much more likely someone will keep your wallet instead of return it...we aren't really such an honorable culture in general, I don't think. So, I didn't trust just turning it into my manager. After work I did some "detective" work to figure out how to get in touch with the man, and was able to return it to him. Of course, he was a bit surprised someone would take the time to do so, and grateful as well. It wasn't quite as easy as it would be now with the internet and social medias and such!
I wish honesty and kindness towards others was the normal every day, in every culture.