Has there ever been a case of an ADULT surviving ...from an airplane crash...

None of the planes were pressurised, very few were in WW2, they were all breathing from some kind of oxygen source and bombers would typically spend 3 to 4 hours at that altitude on route to their targets.

In 1966, an SR-71 flying at 79,000 feet and Mach 3 disintegrated in mid air. Pilot Bill Weaver survived with few injuries: https://www.youtube.com/watch?v=mnEgS3buPb8

As already mentioned, Juliane Koepcke survived free falling from 10,000 ft when the Lockheed Electra she was in broke up in mid air.

There are many sole survivors of aircraft accidents. You’d have to research how many happened at high altitude: List of sole survivors of aviation accidents and incidents - Wikipedia