Yeah I missed his quest completely because he didn't mention it when I got to act 2 and then was never in the graveyard when I got there (which was much later than I should have).
I experienced a related problem in that when I got to act 2 I talked to Gareth and him on the ship and then went below decks. When I came back up both were gone. I expect they are supposed to leave when you leave the ship, but going below decks triggered that early.
