There may be something invovled in the fact that the one group hadn't eaten in 6-8 hours. From what I know about cold weather camping and hiking, you want to be eating high calorie food just about any time you can. Keeps your energy and body temperature up.
In the case of TGRR's avalanche idea though, they could have been asleep, woken up, and bolted when they heard the snow move. So the lack of food might have jsut been a result of that, rather than a cause in itself. An avalanche could also have slammed them off a tree or rock and deposited them elsewhere, with the injuries mentioned.
The radition, and missing tongues, I have no good ideas on. Was there any mention of the other gear found around, if they had food remaining, etc?