Yes, it is possible that the shut of is in the ceiling. I did a job on the 2nd floor bathroom of a sears in a mall. And i had to use a tall A frame ladder in the middle of the clothing section on the first floor ceiling to shut the water off on the second floor bathroom. Luckily the head maitanence man knew where the shut off was. GL... every building seems to be different, ask around with the maitenance guys there, maybe one of them could help you find it..