There's a clue to his name in the first screen. Do you see that carving on the side of the boat?
Rosa can't bend over far enough to see it, but Joey can. Talking to the ghost confirms that his name is Ryan.
How do I get into the locked door?
Your next hint to what's going on here is in the downstairs room, behind that knotty pine wall.
What do I do with this knotty pine wall?
Wow, look at all the money! You can't take it, but you can right-click to look at it more closely. What the heck is GCT? Using Oogle is no help without more information.
Once Rosa opens the locked door and talks to Ryan --
-- he asks if you're from the bank. Maybe GCT is a bank of some sort?
This is a situation for the "Compare Notes" function of Rosa's phone.
How does the notebook work?
Click on "GCT" and "Bank" to have Rosa combine the two ideas. She comes up with the name of a bank, the Grant City Trust. Look that name up in Oogle to get Ryan's whole story, which you can confirm by talking to him about it.
How do I save Ryan?