This is the second time I’ve heard of this, first time for a video. O.o
I have experienced this from both sides of the table actually.
First time I was thrown in to a in-progress game where the Wraith AI was being chased by the hunters except…
I was walking around like a invisible human and I had to kill my self in a Acid pool in order to gain control of the wraith.
Second time was much like in that video. Killed the monster and then had to run around looking for the invisible human but he just ran in to a Acid pool or wildlife and died.