If he dropped these pants to mark the spot he went in, it was a big mistake. It tells me he doesnt know as much as they are saying about the woods. You mark with a tree limb or something. You never discard anything that would help you to survive. Those drawers could'a been torn to cover his head and wrap his feet and hands-the three most important areas of heat loss, especially the head. In cold weather, if you keep your head and feet warm you can sustain in cold weather quite a long time. The hands can be kept a tad warm by flailing your arms across your back driving the warmth down to the hands.
A serious mountain person might leave some signs if he wanted to be tracked later by others.
Small rock piles, rocks arranged in an arrow fashion, marking trees, breaking branches...would be useful.
Leaving pants when one does not have a hat nor gloves is not a good sign. ( It is also not helpful that the local sheriff professes this as a 'sign.' )
Second, I do not know why he did not build a large fire on the road near his car. He had nine days to find dry branches, small dead trees...so he had lots of fuel for a 24 hour, every day and night fire.
The smoke could have been seen during the day by passing airplanes and the flames at night. Plus he could have used the fire for warmth instead of draining the car's gas.