Well, spoiler alert, but is the creature alive or dead? Is the reason he cant fall because he's a ghost? And di his friends somehow trap him in the opening room? If so, how can he leave now? Or is it more of a metaphor for abandonment in the midst of crippling depression?
When I wrote the story, it was that the creature is supernatural kind of like a cryptid. He’s alive and can’t fall because he can float off the ground. The trapping is more kinda magical, similar to a salt circle. His “friends” sealed the building so that he can’t leave (because the creature looked different and creepy) but once you’ve opened the door, it broke the seal and he can leave.
I had in mind a story about not judging a book by its cover but I’ve heard other theories which are really good. The metaphor you said works too even if I didn’t think about it while writing it :)
Thanks for the questions! I hope this answers them :D