The star map found in all those ancient civilizations pointing to the Engineer outpost - do we know anything about how the ancients obtained the information needed to create the star map? It has to have been relayed fairly concurrently with when the paintings/carvings were done, since stars change position quickly (at least when you think in time scales spanning back to the engineer pan-sperming earth hundreds of millions of years ago)...
All of the Earth civilizations who were privy to the Engineer's star system maps would have been given that information, by the Engineers in the worst case scenario, 30,000 years ago. In stellar terms, those stars would have barely moved at all in relationship to the Earth. And seeing that they are created as ART, there would have been obvious differences that would be compensated for using technology once the right stars were found.
There is, of course, some stellar drift on their part and ours, but 30,000 years is insignificant on a galactic scale for those stars to have drifted beyond our ability to identify them, particularly in relationship to each other.
Stellar movement is incredibly slow given the distances between stars; it takes an estimated 215-250 million years for the galaxy to rotate just once.