I placed pins on the locations where Mollie was allegedly seen while on her jog as well as her starting point (JD's home) and destination (Mom's home for dinner). Not sure of the accuracy of the witness sightings or if I have all of them, but if they're all true, then Mollie would have been all over town on her jog and may have gone past Casey's.
Possible Eye Witness Sightings of MT - Google My Maps
Though no one knows what happened to Mollie, I keep thinking of the Jacob Wetterling case. The perp in that case saw Jacob, his brother and friend and went ahead of them on their route, hid and stepped out with a gun. He saw them as they went to the store to grab a video. It was a crime of opportunity and I feel like this is what happened with Mollie. Going near the gas station would increase the likelihood someone from out of the area would have spotted her imho.
Of course, all of this is speculation.