I found them in a city 20 miles away and in a department store of all places. There was a comics rack hidden in the back of the store.
Although I never made great finds of old classic comic books in a hidden place, but that IS how I found many of the most valuable records in my record collection, looking at the loose records that had fallen behind bookshelves in furniture and junk stores, that had lain there for 15-20, or even 30 years! I always took extra time and effort, and it paid off.
I DID, however find many great 2nd hand late 1940s and early 1950s comic books on the 5 cent 2nd hand bargain shelves at the end of the 1940s, and all the way through the 1950s. An, like my record collection, that is how I managed to afford amassing thousands in both collections. And NOW, thanks to CB+, I am enjoying learning about comic book series I had never known about before, or couldn't find at a low enough price, or couldn't afford to buy at "collectors' prices.