I can remember two,m of course these two items were not mine but would have beens someday.

My dad gave me his dog tags when i was 12 or 13.  I lost them at some point.  I really wish I had them now.

The most expensive item I lost was a pair of 10x40 zeiss binoculars.  I didnt understand their value and for whatever reason my mom and dad let me play with them.  I left them at a new home construction site and went back the next morning and they were gone.  

Lost my high school class ring after going to the beach one day, wonder where the heck it's at.  Probably on ebay

Not exactly lost but destroyed. A few years ago I was baby sitting for a little kid and he was in my room looking at some of my stuff. Picked up the binoculars that my (deceased) grandfather carried as a bomber pilot in the pacific during WWII and threw them out the window. They landed on concrete and broke, needless to say i was fairly pissed but it was my own damn fault for letting him get his hands on them.

I lost a 4x20 Colt scope i had on a SP1 shooting at a strip pit.

Left it sitting on a tire and remembered it that night.

I went back the next day and it wasn't there.

My grandparents broke up when  I was pretty young
My grandfather had a girlfriend for 20 years , she was lkie a 3rd grandma for me
About a year before she died she gave me a gold chain braclet for christmas I was in HS at the time , i wore the braclet quite a bit
About 2 years after she died I lost it while deer hunting
I was pretty bummed , however the sumer after that i was riding my 4 wheeler around in the same area  , I was buzzing down the trail to my deer stand and for some reason at 45 MPH  i saw that braclet laying there bigger than life in the middle of the trail
I don't wear it much now as i am afraid ill loose it again and well a big gold chain is a little too Guido for me nowadays


AH SHIT you said never found again
nevermind

My grandfather was an Army Air Corps pilot during WWII (he flew P-47's). During the war the pilots had silk back patches sewn on their jackets. These patches had an American flag with messages in about a dozen different languages telling whoever read them that the person wearing the patch was a downed American pilot and that the United States would reward anyone who helped the pilot return to American forces.

When I was about 15 my grandmother gave me the patch that my grandfather wore during the war, and I gave it to my father. He moved about 5 times since then. Last year I asked him for it so that I could have it professionally framed. We searched every box in his house, but it was nowhere to be found.

Ironic. It usually goes the other way around.

A bunch of military stuff my dad had from his Army/Green Beret days.  One was a coin with his unit insignia.  I have his Air Force one, but the other stuff was awesome.  Lots of gear too.  All ripped from a storage unit that should've been secure.

My virginity.

My bachelorhood

Of all of the things I've lost over the years, I miss my mind the most.

When I was 20, I was staying with my sister and her ogre of a husband.  They lived out in the boonies had had to do laundry at the coin-op.  Anyway, one day I needed to do laundry, couldn't find a basket except for a big one near the door.  It was one of those indian-type grass baskets.  I go down and put the load in, then go have lunch while it's washing.  After I'm done, I look around for the basket, which I had left in the laundromat.  Just a basket, but someone swiped it all the same, the bastard.  Oh well.  Drive back.

Later my sister asks "Where's Brad's mom's basket?"  Brad's mom had died just recently. Uh oh. "I was doing laundry and left it behind when I went and got lunch. Someone stole it."  Her eyes bugged out, and pointed  to an old framed picture of a young Brad's mother holding that same basket.  OH FUCK ME. I thought it was some fucking thrift store special, it was an heirloom and will probably pop up on Antiques Roadshow some day.  That was a major boner.

Quoted: Of all of the things I've lost over the years, I miss my mind the most.

+1

my late grandfather's stamp collection

fortunately, i still have his coin collection... never going to allow myself to lose track of that.