After being disco I too have seen it where I can no longer see the room. What I do is is enter into one of the other online features(recently gtacademy) like the seasonals. I make sure that to go all the way to the track menu to make sure I've entered the online server. I back out and then go back to the lobby menu. Every time the room shows up. To do this takes no more than 90sec. I think of it like when they tell you to reset a modem some say to leave it off for fifteen sec. To make sure it's clear. Maybe when being disco and entering back immediately there hasnt been enough time to clear the errors. Don't know if any of this makes sense or helps...We are having the same problem in D7. It is really hard to find the room sometimes (its the system) We had so much trouble we all backed out and had the host start a public room to finish the last race. We were all able to find the room and get started in less than 5 minutes.
@JLBowler You asked for evidence this is ours.