You cite two examples. I can give you more where no call was made. The fact is, one plausible scenario is crew theft, but just because something doesn’t make sense to a non pilot, does not make it any less or more plausible. The idea that something is “plausable” takes far more knowledge than the average online amateur.
How about another example of one that flew for 7 hours after a fire?
Anyway I agree this is all speculation. This story is already 'stranger than fiction'.