We don't know what happened or how it happened, and the only way we'll ever know is if Mollie lives to tell the tale or her murderer confesses, because if LE had anything, this case wouldn't be cold. Not to be a Debbie downer, but a realistic Rhonda.
My theory is someone who grew up in eastern Iowa did this and has done this before. He jumped off the freeway at the truck stop, headed north into town looking for an opportunity, made a couple laps around the block, spotted Mollie, grabbed her in a split second (east of the carwash) drove to that top right red dot then south to that other red dot and on past, did his evil business, and left the poor girl in a body of water or abandoned shelter.
He's crazy. He wasn't thinking about it's daylight or somebody could see me... no, he looked around real quick to see if anybody was watching when he thought it was a good spot to snatch her, stopped quickly, put the vehicle in park, hopped out, grabbed her, probably threw her in the trunk and sped off.
I think people should search for her way south of that bottom right red dot.
I'm probably totally wrong about all of this, hell I usually watch romantic comedies, not crime shows, so what do I know?! Everyone needs to say a prayer for her heartbroken parents.