Not trying to open another can of worms here but how about this situation. In my area of the country, we have a chain of stores called "Play It Again Sports" and they sell new and used discs if there are courses in the vicinity. When I go and thumb through the used bins, I see a lot of discs with names that I recognize. I have had a friend who was nearly attacked for a disc that he bought at Play It Again Sports. The disc had been lost and whoever found it sold it to the store and it was resold. We have a lot of people around here who find discs and immediately sell them back to the store. But then if someone else rightfully purchases the disc, are they supposed to return it? For the record, if I find one, I call if there is a phone number on it no matter what. If I see a disc belonging to someone who I know well in the "used" bin, I usually call and tell them its there.
On a side note, if you want the disc back, please put your phone number on the disc. There is a guy that plays at my home course, and all he puts on his disc is his PDGA number. No name. No phone number. He expects you to go online, type in his number and look him up, and if you don't he will eat you or attack you in parking lots. And you had better have internet on your cell phone because if you leave the course with his property, then fire will rain down on your head.