I'm going to push back against the theory that it's Lauren sitting in the back of the truck
Part of what I do is 3D Modeling so I'm used to looking at how scales are relative to one another. The information I've been able to find say the back tires are likely on 22" rims (That was on TonyGatto's site) and the Chevy 1500 Short Bed is 69" long. If anyone can correct these numbers I'd be up for hearing it but based on the 30 min of research I have done, those are the numbers I can find. So - based on that ...
It looks like that comes out about right if those are the correct numbers.
Now if we project those measurements on the object in the back of the truck and lets assume for a moment that it is a person ... with its legs bent up. Ill be conservative and assume that based on the image that 'person' is taking up half of the bed or 34.5"
That would make their lower half 2.75 feet long, and that's before you extend the legs (as they are presumably bent up). This would be a 7 foot tall person.
Please check my numbers ... but in all my estimations I went with the more conservative possibility and still end up with someone 2 feet taller than Lauren.
Just for reference the short bed truck is about a foot longer than Lauren is tall. That 58" line would be Lauren's height relative to the truck depth. Just eyeball it and see if that's possible given the proportions of the object.
I'm certain that is not Lauren in the back of the truck.
I don't think it's a person either, but did you consider that a person could be sitting on top of something in the back of the truck?