Thank you for this very helpful addition to the discussion. First of all, yes, that was an odd roommate, but there are definitely lots of odd people in the world. We should really amend fight/flight to fight/flight/freeze because many people *do* freeze. And not only that, the same responses are seen in other mammals, including other primates. We're each wired a bit differently and your experience was in the night, your brain thought it should get rest and downtime, and then you're scared out of your mind by something that you really want to believe is just your imagination.
I think a lot of us have ignored unusual sounds and circumstances, and without dire consequences (but we still did it).