The 10X on the Rocs referrs to a run of KC (Ken Climo) plastic that was run after his 10th World Championship Title. If you look on E-bay, you'll occasionally see 8X's, 9X's, 10X's, that will go for big bucks, since they are not in production anymore, and are pretty well liked rocs. You will see 11X's still for not so high prices, and I'm guessing that eventually we'll see a 12X, since Kenny won his 12th world title this year. I doubt that it will be on the old KC plastic though.
As far as lost discs, and a thread, usually there is, or can be created, a thread under each course's discussion for lost discs found at that course. Sometimes discs can be hard to return, as not everyone puts phone numbers on them, or phone numbers change, etc. If you have a PDGA#, you can look up to see who that person is here:
Just enter their PDGA number in the "search current members by PDGA number". Then, you might get a clue as to who they actually are. The disc you have that says olsen with a pdga number might be AO's--he frequents this board, maybe send him a private message, so you guys can connect somehow.