It might be that he/she came along when Open Mike was out of the room. When the room doesn't have an administrator present, it doesn't show on the room index.

So that the above has some context, Laurel (Open Mike) was having fits with her computer or her connection or her software (choose one or more), and had to leave several times to try to fix things. As I say, Guest's try(s) may have been during such a time.

Dave Oesterreich