Some people, such as myself...ran into a bug where if you dont go talk to Maven Black-Briar right after you speak to Brynjolf (If you go do another quest instead) the quest just completely dissapeared from my log. svcks, kind of dissapointed to see a bug like this...wondering how many quests I've lost because of this.

Did you try "setstage TG03 10"?
I don't know if that works if you have had it and it disappears, but that started the quest for me on a non-thief char.

Ref: http://uesp.net/wiki/Skyrim:Dampened_Spirits