As an Athiest, I thought I would present a short anecdote as a response to the question.
Long story shortened...
I had been discharged from the Navy for about 2 or 3 months and during that time I would bar hop over the weekend. Was great having the freedom to go wherever I wanted to. Well, one night I am playing pool and I look down and I see a bill laying on the floor. I pick it up and low and behold it's a $100 bill. It didn't occur to me to pocket the money, I just thought to myself that someone is probably pretty upset about losing this (If they weren't so drunk they thought they spent it). I promptly took it to the bar and told one of the bartenders that I had found this $100 bill on the floor.
If I had lost $100 in some bar I would think it is probably lost but I would definitly hope I could ask the bartender if it was found and for him to say "Sure, let me see. Yep, here it is."
The golden rule is how I try to run my life, in other words. All we can do is the best we can do, and be good to each other.
By the way, told this story to my girlfriends mother, who happens to be a deeply religious Catholic, and though she praised me for being a good guy, she said she would have kept it.