he's either in the ship yard or outside/inside the museum, if you can't get in go to the shipyard and talk to the confused man with the blueprints. once you talk to him the way into the museum should be clear.

In the future, please refer to the appropriate walkthrough for help getting through the game. If he's left after you beat the Magma grunts, he's gone for a while (until you progress later in the story line). You don't need to talk to him again until then, so don't worry about it.
*Locked* (7/27)