At the very conclusion of Gridania's Main Scenario Quest Beckon of the Elementals...

Miounne: He asked that I give you a message, as well. He said that if you happen to find yourself in Ul'dah, you should pay a visit to the Waking Sands in the Merchants Ward.
Miounne: If you've a mind to head there, you need only follow the Furline south. Now just you take care, alright?
I believe that should be the Lumberline.