I figured that the students had some idea what a "cat cave" was. One girl explained it like she knew exactly what the teacher was talking about. It had to do with feral cats and burrows. (We were in the middle of campus, so I would have thought a cat problem would have been taken care of by the administration.)
Only after one of the neighboring teachers stopped by and noticed the note did I learn what a "cat cave" was.
Our classroom was at the end of a building. Jutting off at a right angle from our building was another building that contained one classroom. A science classroom. More specifically, an anatomy and physiology class.
Currently, they're dissecting. Cats.
Next door to us is their storage room.
On the bright side, I did not notice any foul odors. Although, I was in there all day. Later periods made mention that the room did smell.
At least I was only there for one day.