Wow the age old question-
Give it to its rightful owner, or keep it.
I have a few opions on this-
I give rare discs back if they have names. If its dyed, or a CFR, CE, or ace disk, things of that nature I will give it back. Im not greedy with the disks I find, and to me disc diving is part of the sport. I find a groups of discs in the 6 - 15 range at a couple of spots. I keep the ones without names and usually call back the people who have there names listed. Hell I even got a date with a really hot girl because of a tie dye Jls...Its a way to meet people, and it gives you good game Karma. I also give them away, trade them, ect. Its just part of the game. I think if you are willing to put in the work to find them you deserve them. A lost disc is simply a disc that hasn't been found. I have kept some, lost some, get some back....
Just another aspect of Disc golf.