Factual error: When it's 1969 we see a boy (I'm not sure which one so you'll have to look) riding a Shwinn Sting-Ray Krate Grey. That bike didn't come out until 1971 and they only made them that one year. (00:02:45)
Factual error: Carl tells Alan that his police cruiser is brand new, but the Chevrolet Caprice he is driving is a 1991 or 1992 model as it has "skirted" rear wheel wells.
Answer: The game is essentially "resetting reality" back to the point Alan was first sucked into the game. So it is undoing everything that has been done - including taking away the gun and bullets Van Pelt had purchased.