When possession ends, does the victim automatically detect you if you're in their FOV?

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?

After you leave the body of the possessed enemy, you'll be (as some comments pointed out) behind him.

And he'll be nauseating for 5 to 10 seconds. If you step in front of him, he still won't notice you while puking. It's like a stun effect to them apparently and while they vomiting you won't be their priority.

Confirmed by the wiki :

Furthermore, possession will cause nausea in some targets, which incapacitates and disorients them for a short period after possession ends.

It takes a while to the guard to get things togheter and think about you again (it's the visual transition between puking and the guard getting back up)

If the guard, by the time you left, was facing you and was standing doing nothing, that's probably where you got spotted. Other than that, they won't see you :)