Hunter, unfortunately I don't read Russian. I know most of the letters, but that's it. Yet, what you say is in essence what I learned about the time and the knifes back then as well, so I'll just take it like that.
About the taking stuff as souvenir... It'd be very macabre to take a souvenir from a place, where your fellow students dies. I can imagine something like that with a knife or other rather rare, important and good tools, small enough to just place in ones pocket.
When it comes to other things like the missing spoons and mugs and so on, I'd resort to other causes.
It's a huge chaos, that was found or left by the searchers. There are knifes that should be there, but aren't. The same with ordinary cutlery and dishes and personal items.
The number of the spoons is strange, I give you that. And their disappearance is also not quite ordinary.
*** A story from my experience, going camping with a rather big number of people and everyone bringing their own stuff:
I go camping every summer for more than 10 years now. We usually bring one or two items per person plus some if we get guests. The items for guests only rarely get stocked, because at the end of one week, we end up with more stuff than we brought. Sometimes it's even hard to get everything back to the people that still are with us on the place (meaning not those who came by for a dinner, but who had their tent their with ours). And this is only with people who know what they took, not some friends or family members having to identify what's there.
We also loose things that never show up again.
Having told that: I don't think it strange, that things are missing. Even if we assume nothing was staged (which I'm not sure about), there's a lot of snow, a lot of wind, weeks go by, a group of (sorry) amateurs find the tent and look through what's inside, maybe some of the hikers had some of their stuff in hand and took it down or lost it somewhere on the way. There are so many reasons, why items could have genuinely been lost.
If you take a staging into account, people might still have not looked at the right place...