Was the engineer real?
I don't remember this having been discussed already, but I think I have a valid point here. Enslin had already experienced a couple unsettling moments before he called to have the engineer fix the thermostat. Did he just imagine the engineer coming up to the room? I wonder this, because do you think the evil in the room would have really just let Enslin walk out of the room after he had been provoking it for the first 10-30 minutes that he was in the room? I'm thinking that door never actually opened and that he just imagined the engineer there. Anyone possibly think the same thing?
"Skank!! You sank my destroyer!!"