Disappointing, and one huge question for me

Rating: 3/10 (10 August 2012)

As many others have stated, this film was really disappointing, so I won't rehash what others have already said (and more eloquently, I'm sure).
Along with the other plot holes and "Huh?" moments already pointed out, there was one thing that really bothered me and totally took me out of the movie. Apologies if this has already been pointed out, and this does contain a spoiler -- David says there is only one "being" alive, in stasis, and at this point in the film, we know that the beings are human-like and wear what, for lack of a better description, amounts to an elephant-looking space suit over their humanoid heads and bodies. OK, now, David brings the one still-living being out of stasis, and he proceeds to kill Weyland and rip David's head from his body. This being then later goes on to attack Shaw in the Prometheus, until her squid-baby attacks and kills it. OK, so here is my question -- WHO THE HELL WAS THE SPACE JOCKEY THAT DALLAS, LAMBERT AND CAIN FIND SITTING IN THE CHAIR WITH HIS CHEST BURSTEDED? Remember, they showed the chair coming up from the center of the room where David gets beheaded and all, and the chair is empty. At one point after that, the being sits in the chair and the armor encompasses him. OK, so far so good. But then the being goes after Shaw in the Prometheus and dies, so ...
???????? Did I miss something?