BBM: I tend to agree with you, although I haven't ruled out completely random.
If Jessica did not normally work Friday nights, the perp must have been driving by and noticed she was working, or just happened to go there that night, and started to formulate his plan.
We know he was there at least 2 hours prior to the abduction. Did he stay near the gas station the whole time?
Did he watch the various men engage in conversation with Jessica?
Did he drive around to other gas stations or places looking for a victim, and decide to go back near close?
Why not wait until Jessica went to her car to leave for the night???
Or maybe he came by a time or two when she was working and decided she was going to be his victim.
It's hard to say if Jessica was the intended target or any lone female employee that he could get his hands on.
I'm thinking this is very possible. Maybe he chose this gas station because it is so isolate from everything else.