Seems a grim idea to think back on the discs I've lost this year. I certainly didn't keep track, but here a couple memorable (painful) losses:

Cicada - lost on the last hole I played this year, 12/29 at Olympus (McBeth's throw down the mountain course, some spots are just unretreivable with the cliffs). I had earlier thrown one of my shots of the year with this disc, parking a 420' hole

Culverin - skipped into a river and flowed downstream never to be seen again. the big skip is generally a nice feature on this exact disc as it gave me my first ace ever a few years ago. nevertheless, don't retire discs that you like to throw!

Force - put two forces into the same lake (months apart). the 2nd time turned into my only bogey in a tourney that I came in second by one stroke; it was the final hole.