I decided to go down into the old city in Neketaka Quite early and ended up exploring it quite thoroughly, at least up to getting the conch down there, and I ended up opening the hidden temple door and entering Delvers row that way. In short when I tried to start the Cornetts call quest from Dereo I got the option to show him the cornet I already had, he sent me back down to the temple to find some mosaic in a hidden temple, eventually I figured I needed both ,however, even with both cornets absolutely nothing happens when I walk around the old city ruins. I find a mural with 2 conches on it, I have exhausted every dialogue option with the woman Dereo sent and have walked along every possible inch of the ruins. I'm guessing that by opening the door from the wrong side before I got the quest it has bugged the quest. So I have had to backtrack about 4 hours..... Just thought I would put this up here in case other people have the same problem.