Is there some sort of numerical catalog of 'rooms' ?

[Lemuel]

In another MUD I played, you could type in the command ROOM and you would get back a number that would uniquely identify the room your character stood in.

This was especially helpful when reporting bugs and similar instances when you wanted the Admin to know which exact place you were talking about, especially when some rooms are practically identical in description.

[Rias]

The bug command automatically reports the identifying name of the room you're in when you use it, and GMs see it along with the common name whenever we see a room.