For those of you who haven't been with Zombie Roomie for the long haul, or those of you who have forgotten... Drew was John's roommate before George
Also, before George ate him
But until now his return, as a ghost, hasn't been common knowledge to all of John's friends. John and Bill hadn't been hanging out for over a year
, mainly due to the search for George's soul... so it may have just slipped John's mind and he didn't inform Bill of their old friend's new ectoplasmic existence.