I've heard the "you're not dead until you're warm and dead" saying before, but this is still amazing. Hopefully we can keep saving more people.
This sounds like a spruce trap, though I wish they'd explained it a bit more. A spruce trap is snow buildup on the branches of a tree such that it looks even with the rest of the snow. But in reality there is a lot of air, and a person's weight causes the whole thing to collapse and suck the person in. I understand they're very difficult to get out of.