The analogy I think of is with silent film. The nitrate film that they used back in the day was highly combustible, for this and other reasons most silent films are lost. "Dawson City: Frozen Time" is a very good documentary about a stash of films that was discovered in the Yukon (used as land fill for a swimming pool!). Many silent films only survive from this find, recognizable by their water damage. The other films that were part of the same movie theater inventory were deliberately burned or thrown in the river, people didn't want to store them any more.
The analogy with OA is stories broken up and pages scattered. Buried in people's collections, who may not even know what they have. No doubt some of it stuck on shelves in garages or in attics, discarded when the owner passes away.
Imagine if all we had left of classic EC art was the tired old original comics. Much survived because Gaines kept it together, but that will be scattered as well as the people who got it cheap in the eighties liquidate their holdings. I'd like to think the best stories will be preserved intact, but when I hear that the recent buyer of Master Race only heard of it a year ago, I am not optimistic.