A L.A. radio talk show host was making much of this: “Who would ever go on ahead and leave their partner behind?”
It’s done! People do exactly this! One partner can’t move any longer, and the other tries to go on to find help. It may not be the BEST thing to do, but it isn’t intrinsically stupid or wrong. If one partner is still fit to move, he MIGHT succeed in contacting a rescuer.
I’ve been in this situation myself, when hiking: one of the party simply could not continue. So we cached him in a comfy place, shady, lots of water, and went ahead to get the car and bring it back to pick him up. It isn’t the wrong thing to do.