@Sage - Vadar knew about Palpatines "traitorous nature" before this game in the books, its just he is once more shown.
Subject 1138 -- Galen Marek.
- He could've been cut off from the force when he used such a huge force repulse against palpatine or He was in a near-death state, Hell there are people in the real world who "Die" but then can be brought back. Don't forget there was also a Jedi trance that made the heart beat so faintly that they appeared dead (I don't presume he has this however seeing as how it was an ancient trance used by few).
-Do to his near death experience he also has a coma or vadar worked on suppressing his memory with the technology at Kamino. While at Kamino vadar does clone him as seen in the trailer. Galen finally heals and right now currently a blank slate, due to his coma and the new memories possibly imprinted, does not question he is a clone. When he does have the visions he begins to have doubt and that is when vadar tries to keep him under control by telling him he is a clone. The clone begins to believe his master for a moment until his memories begin to resurface more and more. The final stepping stone to realizing that Vadar is not telling him the whole truth is in the Trailer "Vadar has betrayed me for the last time" this is when he begins to believe he is the true galen but with no proof to go on he goes off to find himself <Follows with the Storyline as to Find out if he is a clone or not> so he goes for Kota in hopes to also perhaps find Juno at the same time.
It would seem it would be going ^ that way to me...but they might do something slightly diffrent...