AC: Brotherhood after credits Question (SPOILAHS)

Hey PS3ers. It's been a while since I posted here on GS. I just finished AC Brotherhood and boy the story is so interesting. Can't wait for another AC to come. :)

Anyway, on topic. In Desmond Miles's wiki, it's stated that" As Desmond started to go into shock, he was put back into an Animus byWilliam M.and another, unidentified person. During this session, Ezio andLeonardo da Vinciwere seen to have discovered a smaller vault in Rome. When Ezio's DNA was activated, a set of coordinates intended for Desmond were projected: 43 39 19 N 75 27 42 W. After reliving more memories, Desmond's condition worsened, and he entered a comatose state. ".

The thing is, after the credits, I went back into Ezio's hideout, haven't seen Ezio and Leo discovering some small vault. Is there any particular place in Rome that should I be going to? Fill me out guys.

I'm worried about the direction devs are taking with DLC. I'm a story-driven gamer so I'd hate to go through a DLC story pack with half the commitment and terrible gameplay (compared to the main game) just so that I can see more of the story. I already bit the bullet with Mafia II. Main problem is I can't sell the pack afterwards.