You left me hanging a bit. I'm guess it was a dead head, but if not,

1. Was it just his head or the whole body?
2. Was he alive or dead?

This could have been a real person that was detained somewhere (under a different name) and his relatives sold all his property and home (Apt. 311) since they thought he was dead. After 1 years of absence, they can declare you legally dead and dispose of your property, even if they haven't found your body. This could be the source of a lot of "haunted house" stories. From your perspective it feels like someone or something is "gaslighting" you - trying to mess with your mind by showing they can invade your home any time they want. Your "ghost" may be a real live person, possibly homeless, going back to the last home he had (maybe a sleepwalker) for a nostalgia trip.