User blog comment:Ichigostop/Isn't Shanks supposed to already know where One Piece is and how to get to Raftel?/@comment-3326484-20110201221921

I personally think that Buggy and Shanks may have left the crew to start their own adventures before the crew reached Raftel. I can definitely picture Shanks telling Roger he wants to live his own adventure, and leaving. Buggy left because he wasn't going to let Shanks out do him.