I've lost a couple that still make me frown.
When I was 16 my grandmother gave me a knife that she and granddad had bought from the Holley factory across town from where they lived in Lakeville, CT. I don't know what they paid for it. It might have been a two-dollar knife or a five-dollar knife, but since it was made prior to 1950 it's hard to judge, and Holley hasn't made knives since 1949 or so.
It was a white bone handled carbon steel (very like CV from the patina it took) Wharncliffe Whittler. Main blade was a two-inch Wharncliffe, and at the other end were twin pen blades. The knife was unholy sharp, had an alligator's snap, and was just about the perfect size and shape for a gent's knife.
I took it with me when I joined the Air Force. When I returned from England in 1972, it was somehow not among my personal effects. The last place I can clearly remember seeing it was in Bedford, England. I was carving a small figurine with it. A swan as I recall.
To add insult to injury, one day a few years ago someone used the word "Wharncliffe" to describe a whittling knife, and I had no idea what that was. I Googled it and stumbled on a picture of a recently sold copy of exactly the knife I had. The sale involved the same design but with black ebony handles. In all other respects, the knife was the one from my youth. The final selling price in that auction was $400.
The other one that brings on the melancholy is a mariner's rigging knife that I picked up at a little shop in Lisbon, Portugal.
The thing had an absurdly sharp sheepsfoot blade and a marlinspike, and a brass bail that also served to unlock the blade. Very similar to the Buck Knives version of the knife. When I flew back to England in 1983, security said I could take my Imperial four-blade scout style knife with me on the plane, but they bagged and tagged my rigging knife, saying I could pick it up once I landed.
In the madness of going through Customs & Immigration, I forgot to claim the knife.
*Sigh*
There may have been other losses, but none are missed as much as those two.