I had the "Pleasure" of spending the night in the woods a few years back while trail riding in Michigans U.P..
We all rode in a huge group, I carried alot of gear becuase I am always 'Mr. Prepared For anything" on this particular trip we had some rookies along. I stayed at the back of the pack in the A.M. to babbysit them, and finally I got sick of that and rode in the front of the pack to play with the big dogs.
We are out in the middle of the Ottowa national forest and I break a chain, I am off the sled waiting for the rookies to show up and they pass right by me! WTF??? it was 20-30 miles before the lead end of the pack knew someone dropped out becuase the rookies never stopped. I wasn't goingto hike it out in the dark, so I figured I would say put until found or morning.
Anyways, the stuff I carry in the flatlands may be of help to you guys at high elevations too.
I keep 4-5 mylar space blankets, Parachute cord, Dry packet hand warmers and liquid fuel warmers, Zippo lighter with spare fuel. (leave the bic's at home, they are useless under 40 degrees) A magnesium bar with attached flint for fire starting, a knife, pliers, and a packet of dogwood fuzz for tinder to start a fire. All of this is kept in foodsaver vacuum bags to keep it dry and compact. I also have aspirin, tylenol advil, some patch kits and ace bandages for minor injuries. a few chocolate bars is highly recomended. It sucked but nobody ever razzes me about carrying too much gear anymore. And I just about killed the rookies that were on that trip, they never rode with any of us again!
being in any elevation, I would be concerned about water or a way to melt snow for drinking water.
Good luck, I hope it never happens to anyone, but at least be prepared.