I was going for ghost in a level, and had no way across a courtyard. I ended up possessing one of the guards as he was going past, then going towards the door. The possession ended just shy of the door, with me in front of the victim, but I didn't hear the chime for being detected, so quickly opened the door to the new area. At the end of the mission, it showed I'd been detected once, but I didn't think anyone else had detected me.
When possession ends, does the victim automatically detect you if you're in their FOV?