When you get Ramuh & Co, there are two possible ways to leave the room:
1) Talk to the PCs standing at the exit, which triggers a long cutscene of everyone talking while climbing down the tower, and ends with talking to the entire party by the Zozo exit.
2) Accidentally walk past them, fail to trigger the cutscene, walk down the tower manually.
Sounds to me like you went with option #2! If that's the case, you'll have to go back up to the top of the tower to the room where you found Ramuh and talk to the PCs there.
If it's not that, then I have no idea.