so how about the driver's or drivers' actions / lack of situational awareness?

From the OP: "Ye Meng Yuan, a student from China, was covered with fire retardant foam"

Early photos and video of the crash site show that there was a lot of foam around the aircraft and it appears to be feet deep. If the girl were unconscious, lying in the foam, visual sighting would be impossible. That is why rigs are being fitted with heat sensors.

how someone could have missed seeing her. It was broad daylight, no fog or visibility problems.

Such a horrible tragedy.

I have driven large vehicles, and to make a long story short, it is almost impossible to see anything more then the board area, i.e. no way you can see as much as a person in a car. The problem is the vehicle are that massive. This is why in most non-emergency situation you try to get some people on the ground to guide the driver where he is suppose to go. Given that job of these trucks, I am NOT surprised of the Federal Requirement to have heat detectors, it may be the only way for the driver to detect a person around the truck (Other then having people on the ground as the truck moves into position).

But at least one of the videos I saw showed the plane covered with foam and people walking around it. The foam had to be 2-4 feet deep in spots and could easily have covered a person lying or sitting on the ground. In later shots showing the burned out plane, the foam had either dried up or had been hosed down - those are the shots most often used since they gave a better picture of the carcass of the plane. But they are deceptive since they do not show the amount of foam that had been sprayed over the crash scene.

I never understood, how a spotter on truck didn't see a body, probably strapped in a seat on the runway. Maybe there is just too much chaos to expect that in a situation like this.

to not equip that truck?