Just to show how much more complicated this could be:

the last report is by his friends seeing him near the cables from Trail Camp. That is a long way, even with binoculars. People often wear clothing that, at a distance, looks the same.
We are depending here upon people who just came down from 14,000+ feet, and may still be affected by oxygen deprivation....which is a true description of their physiologic state.

In this paper, it is pointed out that red visual threshold is much more effected than blue. And personally, I think everyone's clothing looks black at 1/2 mile:

http://www.iovs.org/content/10/5/323.full.pdf

I haven't heard of any "lost hikers" this year down in the Crabtree area (hopefully due to the new signs), but it is certainly in the mix at this point.

I can't fathom his being in the 2.5 mile discussed, with so many experts searching the area.

On the other side of Wotan's throne?

By the way, the hypoxia issue should be taken into account when judging the decisions of his fellow hikers.