Unanswered Questions.

Something that I've not seen anyone pick up on yet. when they first trigger the hologram it shows a group of engineers run into the chamber with the giant head seemingly running away from danger. One doesn't make it and ends up getting beheaded by the door. 2000 years later no-one has moved the body or the head. So what happened to the other engineers that ran ahead of him?? From memory (and I may be wrong here - need to see the film again in a week or so) doesn't one of the scientists comment that one of the murals or walls looks more like a door. So my guess is that this is also a portal through which the other engineers escaped - maybe to their home planet ??