Not only one, by any means. It was rare to find the one in their room. And nobody knew where they were.
That's because they were running around between the "copy room, teacher’s room, SPED room, SPED office, library, guidance office, etc." and even if they'd told someone where they were going (not that most other teachers would want to know or would remember) they'd probably be at the next place by the time you got to the first one.
The other places I'm liable to be during my "prep" period are: in the main office, covering another teacher's class because there isn't a substitute, or attending a Student Support Team meeting.