Here's one from back in my Uni days - Swansea 1990.....
My girlfriend and I were shopping in a supermarket and we were really skint.
I spotted a purse on the floor and (being crowded) I pointed it out to her and waited till nobody was about.
I'm not sure what I planned to do other than pick it up but out of the blue a middle aged bloke picked it up and tossed it into his trolly. We followed him round into the next aisle to see him hand the trolly to his wife, pocket the purse and head out of the building.
I went straight to the security guard near the entrance / exit and told him what we'd seen before carrying on with our shopping.
About 15 mins later we were approached by two police men and the security guard to say that they had stopped the man who admitted lifting it.
Cut a long story short - I was led to a back room where (with the police) a lovely old lady thanked me. She said she only had ten pounds in her purse. She offerd me the £10 and I declined. She was worried sick about loosing some family photographs.
The police asked me if I could spare half an hour or so to make a statement and ID the bloke. I agreed but explained that I'd have to let my girlfriend know as she was still doing our shopping. The supermarket manager told me to go and tell my girlfriend to finish our shopping as it would be 'on the house'.....
Needless to say our humble £10 basket became a £250 trolly.
I still don't know to this day what I would have done with that tenner had I picked up that purse