I didn’t even own a 10mm socket in the ‘70s, so I also never lost one then.Funny thing, I never lost a 10mm socket until about 1985. I can tell you honestly, I never lost a 10mm socket in the 70's.
On a slightly different note, all early 80s and 90s GM cars used 11mm bolts on a number of places, but no metric socket sets regularly available had any 11mm socket in them. I had to search around to find one separately.