I may not be the most aware person in the world and lack a fair ammount of common sense, but I think I would notice if someone was living in my house.
I see not so dead people Hiding in the closet, coming out when the guy was not home. How could you miss someone living in your closet?

My wife recently told me a story from her child hood. She had a friend in highschool, ( when I heard the story I thought it was elementrary school), that she wanted to ride the school bus with. But her father did not allow them to have friends stay over during the school week. This did not deter my wife. Her friend came home with her. Their master plan was for her to hide and sleep in the closet. Unfortunately her father through a wrench into the plans by coming home sick early from work. She was not smart enough to think he might notice a difference in her behavior, ie staying back in her bedroom instead of watching tv in the living room. So he comes back and pops his head into the room to check on them and the friend darts back into the closet. Busted. And in less then a year.

The man had to have cameras installed in his house to catch the woman. And he only became suspecious the past few months when he finally noticed food missing. I love food, I would have noticed missing food much sooner.