In my case, the ringtones were on the SD card. Previously they showed up in my ringtone choices; now they don't. I had to copy and move them to the ringtone folder on the phone itself. THEN I had to go back through all my contacts and re-set those with particular ringtones. GRRRRRR! Possibly the result of a recent software update?
Fishingcat, I would have to agree. It sounds like an update of some sort may have caused this issue, especially since it removed all the ringtones from your phone. Has this ever happened before with your ringtones?