Might help. Seems a bit expensive for what it is, a pole-less dome tent with a plastic window and a pair of hand holes. But wet, exhausted and washed up in a cold rain and lacking other resources I could see where it might be a valuable resource.

Quite a few of the European mountaineering backpacks from the 30s, a few even to this day, are designed with a long cylindrical main bag and extended cuffs so that in a pinch they can be used as a half or three-quarters bivvy bag. Either as an emergency backup to, or supplement, for a sleeping bag. You would employ them by taking out your gear and stuffing your legs into the bag. The popular terminology, as I understand it, is that a half bag came up to the hips or waist. A three-quarters bags would cover everything from armpits down. Either could make a very significant difference in staying warm. Especially if you lost, or soaked, your sleeping bag.