Probably stuck in a shed, barn or other outbuilding that is infrequently used by the owner. Cat goes in while door is open, sleeps, resident leaves and closes door, cat is now stuck. The cat however will hear an approaching human and rush the door when it's opened next.

It happens to cats all the time when you live near farms, you either get used to it or learn to keep your cat indoor.

(If you only ever 'adopt' stray cats, it's a reasonable coping strategy to consider their presence somewhat ephemeral)