OK...now I've mulled over the significance of leaving the shoes with her body. Also, what mia g said about her being 5 miles from the Hitchin. I've made a more detailed theory.
She left Hitchin by foot and walked a bit onto the road, and hitched a ride with a trucker. She got into the sleeper cab and set her shoes down on the seat beside her. She asked him to drop her off to Ellis PU, and he said OK. Minutes after, he pulls the truck over to the side of the road under a false pretense. Maybe, he told her that he wanted her help changing a tire. So she was about to climb out of the car, and then he somehow alarmed her or surprised her. I wonder if he could have fired a stun gun or something like that, not at her, but around her. He assaults her, strangles and beats her, all in the sleeper cab. It looks like he just pulled over for innocent reasons. Then, he starts considering dumping her body; he just throws (horrible, but it doesn't look gentle, or look someone trying to undo an act) her body out the side and is about to move on. He sees her clothes are wadded up alongside her shoes in the sleeper cab. He never touched the shoes, but he's worried that his blood/hair samples will be on the clothes. He tosses the shoes out of the side as well.
I wouldn't be surprised if he did dump her clothes in a dumpster in another state. I doubt her murder would be widely reported across the country, and I truly think her killer was an impotent trucker.