After doing the escort bit and coming face to face with the Balrog, you talk with Thili and are supposed to be transported to the 21st Hall, but the dialog ring disappears!
If this does happen to you again, try running back towards the Bridge -- there should be a failsafe in there now that will recognize that it's supposed to teleport you, but it might only kick in as you approach the Bridge coming from Thili.
MadeOfLions
The Lord of the Rings Online Team