I used to work at a "bakery" in the mall that mostly sold cookies and cookie-cakes. We only make the cakes by order (although it only has to be 15-30 minutes in advance), and keep all of the completed order forms for about a week in case there are any issues, discrepancies, etc.
One day, I am helping customers as usual, and this nice couple hands me a $50 that they apparently found in front of the cash register. I was pretty stunned that not only a) did someone drop $50, but b) that this couple didn't just snatch it and run.
I took it to the back, and noticed it was triple folded in a strange way; not enough to be done on purpose, but too creased to be from a tri-fold wallet. I remembered one older gentleman who had just payed for a cookie cake about 5 minutes earlier with a card from a money clip, so I went to the completed order box, called the number and got his Wife on the phone (W).
Me: Hi, this is Name from Store, could you ask the gentleman who picked up this cake to come back, we think he left something at the counter.
W: He's still in the mall, I'll go ahead and let him know!
[couple minutes later, gentleman (GM) arrives]
Me: Hello Sir! Have you happened to noticed anything missing?
GM: Well, I got a call from my wife saying I had, so I checked everything, my keys, clip, phone. I'm pretty sure I've lost a $50 bill actually.
I pulled it out of my back pocket, and he is completely dumbfounded.
GM: That's incredible.. You know you didn't have to do that..
Me: [something trying to sound noble, can't quite remember]
He ended up handing me a $10 as a Thank-You, which was my largest tip over the 2 years I spent there. I felt obligated to find the money's rightful owner because of that selfless couple who didn't take it to begin with because I know 100% that I would have snagged it immediately.