space jockey question

spoiler now not sureenhow directly related prometheus and alien are.... but assuming that its the same planet and loccation that they visit in alien.... shouldnt the space jockey have been sitting in the chair when he died /chest exploded ? not in the vickers retreat room..... thought they wouldve bridged that gap at least....but then.... its damon lindleoff all over.... so i half expected no answers and a cliff hanger to a sequel... as per lost. overall disaapointd and im not even a big alien fan but expected that theyd be a consistent plot at least