Maybe they set the car ablaze and while the fire was still small, she was trying to back in / out of an area to get to safety and did the damage herself backing into another vehicle or tree or something. I'm assuming if a car did hit it , then any evidence of that other vehicle was ruined by the fire .
Glad you made it Ocean
Here are some random thoughts from a user in Mississippi (do not live in the area or personally know anyone connected with this awful crime or those investigating.)
1. The horrific aspect of the burning has generated all sorts of contradictory reports about flammable liquids being used, and moreover the TYPE of flammable liquid which may or may not have been used. I don't know about other parts of the country, but here in MS a lot of times when people say "Lighter Fluid" what they actually mean is "charcoal starter." Real "lighter fluid," I would think, is a fairly exotic product that possibly generates a traceable purchase. "Charcoal Starter" on the other hand is quite common and could be expected to be found in myriad pickup trucks all over the area, particularly in the trucks of hunters / outdoors-types, as well as by those bent on burning evidence to conceal evidence of a crime.
2. Which leads to my next point: I agree, like many of the posters here have stated, that the burning is an attempt to cover up evidence, either of a sexual assault or of what the perp(s) assumed to have been a dead body after a physical assault.
3. There have been reports of a laceration and/or trauma to Jessica Chambers in the head area. (These reports appear to be contradictory, inasmuch as this is stated in some reports, left out of others.) However: It would seem at least highly unlikely that anyone would use immolation / burning as the "MO" of causing her death, unless the killer(s) assumed that she were already dead or at least unconscious. Here again, I am assuming the killer(s) thought that she was already dead, as burning would be EXACTLY the sort of thing that would seem likely to revive a (merely) unconscious victim. To my way of thinking, any killer(s) who mistook Jessica Chambers being unconscious with her being deceased is an inexperienced killer, even if he (assuming it's a he) is more experienced at battery or physical / sexual assault. There is apparently one preliminary autopsy report "out there," but the details as to other injuries or the exact primary and/or secondary cause(s) of death are not being released, at this point.
4. The cell phone. It strikes me as significant that some effort was made (by someone) to discard of the phone separately from the phone battery and/or internal sim card (or whatever it's called), all of which were reportedly found some distance from the exact site of the burning car. To me, this rules out any "oops" cause of death through drug use, faulty equipment in the car, etc., as it seems HIGHLY UNLIKELY / coincidental that someone would take apart a phone and discard of it away from the car before an accident. Please note that by mentioning drug use I am in no way trying to shame/blame the victim, and moreover I have not read of any report that Jessica Chambers ever engaged in any illegal activity whatsoever. But; even if a drug-use or other accidental cause existed for the fire, there would be no reason for anyone else on the scene to discard of the phone. Also, that someone would think that merely getting rid of the physical evidence of the phone itself would deprive law enforcement of tracing her phone's activity prior to her death suggests an inexperienced or at least naive perpetrator-- you know, PHONE RECORDS.
5. Finally, I hope that the Panola County S.O. will consider calling in help from the MBI (through the MS Dept. of Public Safety) or if possible even the FBI. I have no doubts the local law enforcement are earnest and dedicated and working hard to solve this, but this is a complicated case with all kinds of "stories" out there already; and it's going to get worse before it gets better. My heart goes out to the families and friends of Jessica Chambers and all victims of violent crime, and I sincerely hope those responsible for her death are brought to justice ASAP.