the things to think of for concealment when i was in the military were:
shape
shine
shadow
silhouette
spacing
surface
movement

the worst is shine; people send signals to aircraft with a little mirror. in the british army they gave us everything in camouflage, then issued shiny mess tins!
concealment is a fantasy option, can anyone give an example when not being findable was helpful in a natural disaster?

but you specifically say 'I guess my question is more for the EOTWAWKI scenario.'
and the only realistic scenarios that could bring the US to it's knees is a nuclear war. In which case why hide yourself?
from who? why would they be looking for you? "The population has just gone through the floor; there are cities to empty, but we'll go into the woods and if we find someone in an orange jacket we'll have him"
the only reasons to conceal yourself in a disaster is because you are intending on doing something criminal. then running away and hiding. otherwise you want to be as visible as possible. no one is going to come for you if you are trapped by fire/rubble/water if they don't know you are there.
The Sock