A working battery is also useful for starting a fire as long as you have a pen as well. (They may not have known that)
The flashlight was 'discarded' around the 3rd rocky ridge down - could be that the holder tripped on the rocks dropping it, not necessarily in panic.
I agree that a beacon although possible is less plausible - If I want to return to the tent I have tracks to follow uphill which I can spot with my flashlight.
There is another reason for leaving a flashlight behind. If you are being followed in the dark but at a distance when your pursuers arrive at the flashlight and pick it up this will signal their distance to you. Personally, I do not think this likely but it is a possibility.
It is possible someone fell as per WAB's theory but why wouldn't one of the other hikers pick the flashlight up again. Especially if it was still on, it would be easy to find?
Regards
Star man
Yes you're right if it was still on it would be easy to find which suggests some possibilities:-
1) It may have malfunctioned when hitting the ground and was not immediately able to be found. - I've dropped flashlights in the past and it's gone out only to come back on when picked up.
2) It may have landed face down in the snow with no light showing and was not immediately able to be found.
3) It may be that the person who found the flashlight inadvertently switched it on and off and mistook off for on - I think this explanation unlikely.
4) If left ON the battery would have surely drained. Sometimes batteries come back to life. Let's take the simplest zinc/carbon battery as an example. If you take a zinc rod and a carbon rod, connect them together with a wire, and then immerse the two rods in liquid sulfuric acid, you create a battery. Electrons will flow through the wire from the zinc rod to the carbon rod. Hydrogen gas builds up on the carbon rod, and over a fairly short period of time coats the majority of the carbon rod's surface. The layer of hydrogen gas coating the rod blocks the reaction occurring in the cell and the battery begins to look "dead". If you let the battery rest for awhile, the hydrogen gas dissipates and the battery "comes back to life". If the hydrogen sits on the rod and there is no power drain any remaining charge in the battery can remain for a considerable time. It may be that the finder by picking up the flashlight and jiggling it dislodged the hydrogen allowing the flashlight to come back to life.
If the flashlight was being used prior to being discarded I assume it was being held by someone at or near the front of the group to light the way. I wonder who was leading the way ?