There are three in all. One of them is on Guldo. The other is on a guy leading into Guldo's room. It's impossible to miss him, seeing that the doors next to the "666" can't be opened. He is in the room with the switch that turns off the power to Guldo's area. I believe that the last one was on a guy wandering around in the hallway just past the stairs when you got to the fourth level of Coldwater. I'm relatively certain that he had a flamer. Anyway, short of a bug causing someone to not show up, it would be very difficult to not encounter the other two PA suits on the way to Guldo. You may have inadvertently killed the guy and not realized he was wearing PA.
