I used to own a copy of South of Heaven by Slayer on vinyl. I bought it in a sale from the guy who at the time owned a record shop in my home town for £4 (1989) I don't know what happened to it, but I wish I still had it, because Satan wants me to still own it.
My LP/45 collection is not lost, but it might as well be. When I moved into my house in 1997 my parents dropped off my LP's soon after. I wish they hadn't. They would've been much safer in the dry cellar than my crawl space with no temperature control for the last 15 years. I'm afraid to see what they look like now. It's been almost that long since I've seen them. I may have taken them out years ago feeling nostalgic but quickly tucked them away without giving them a listen. The last LP i got was probably 1984 or 85. Wish I could remember what it was. When I joined the NAVY in '85 cassettes were the way to go.
A shoebox full of baseball cards (circa '71-'76) disappeared when we moved in '79. It bothered me until I started to hate Major League Baseball a few years ago. I still wouldn't mind having Oscar Gamble's huge 'fro back, though.
Actually I lost half my vinyl collection about ten years ago during a flit. Still not sure what happened, but among some of the items that went walkabout were the last 7 singles of the Wedding Present Hit Parade 7" releases.
Kiss Alive! It was the first rock'n'roll album of my own, the kids next door were forced to give it up. I saw one at a flea market with the same wear pattern, but it wasn't the same.