Check behind , and under the bookcase. My girl is only 223g, so i can picture the size of your Bp. you won't believe the small space they can get into. and how small they can make themselves look. Even if the bookcase is up against the wall , the molding around the floor might just give him enough of room to squeeze back there. Also even if their is only an inch or so of space under the case look there. Check the corners of the closet and in anything that is on the floor. You would be shocked to know where these guys can hide. Keep the room door closed and put a towel across the opening. with the food in the center of the room. Also start checking the rest of the house just in case. Good luck