I read an interesting article about a mysterious phenomenon that happens to solo climbers who are hurt, lost, or very tired. It invoves a human's capacity to conjure up a companion when one is most needed in a survival situation. T.S. Elliot wrote about it:
Who is the third who walks always beside you?
When I count, there are only you and I together
But when I look ahead up the white road
There is always another one walking beside you
Gliding wrapt in a brown mantle, hooded
I do not know whether man or woman
-but who is that on the other side of you?
I seldom solo and have never experienced this. Have any of you?
More information on this can be found in a book written by explorer and survivalist John Geiger- "The third man factor: surviving the impossible". He has document hundreds of these incidents.