Oh man, it is so much fun, but you do have to deal with lost disks and water hazards. There are a few courses out there where all the disks collect and get exposed when the water is low. It is nice that your friend returned the disks that he could. I don't usually mark mine unless I really like them. That way people don't feel so obligated to return it if they find it. What might be cool is having a little tag that you could register with the factory to pay for shipping to you if it is lost. That way people could just put the lost ones in a mailbox to return them if they are tagged, kind of like lost sets of keys. They are really not that expensive to replace though, so I'm not sure if it would be worth the effort unless it was a favorite disk.