There are two possible explanations:
- The gate was moved between the film and "Children of the Gods."
- In the SG-1/Atlantis continuity, the gate was always stored in Cheyenne Mountain. The change is merely a retcon.
Considering the facility the Stargate is stored in is practically identical in both (in both cases its a former missile silo) and there has never been evidence that the gate was moved, the latter seems to be more likely, especially given other contradictions between the film and the series.
Behind the scenesEdit
There is no Creek Mountain military installation in real life, but Cheyenne Mountain Complex is an actual military base. Due to the great similarity between the two, it seems reasonable to conclude the former is merely a filmic clone of the latter. In fact, according to the Internet Movie Database, the entrance to Creek Mountain used in the film was reused from the 1983 movie WarGames, where it doubled for the entrance to Cheyenne Mountain.