Meet Clarise limehouse in the lounge, get she shirl off her and trade it with vlad for the note book, or necklace. If your having trouble getting off the ship, hang around officer morrow or play blackjack with the man in the smoking room.
You may have missed something earlier in the game, however.
The real necklace is in the ornament on the desk in sasha barbicon's room.
if you don't have the painting at the end, than go down the second class stairwell, you'll run into the person who has it.
I may already have it, but at the start hide the ruibayat in another coal bunker and pick it up later, so as to trick vlad.