Do corpses of unique enemies/NPC disappear?

I wanted to collect all paragon gems.

However, I already killed one of the ice giant and I couldn’t find that guy anymore. No problem. I just watch youtube video and go to the location of the giants. Sure enough, the corpse is still there.

Now, I want to do the quest that requires 8 dragon priest masks. It turns out, I do not have krosis.

So I go to shearpoint https://elderscrolls.fandom.com/wiki/Krosis

Voila, no Krosis. I must have killed him a long time ago and I have no idea where I put the mask.

Now, I wonder why Krosis body isn’t there?

So I just did things like

player.moveto 000F8A48

out of curiosity

No reference id. Krosis is really gone. Of course, I can just add Krosis Mask using console, but I want this to be more lore friendly.

Note:

player.moveto 000F8A48

actually move my character somewhere if I am near shearpoint but not when I am far away. I must be missing something. I don’t see his corpse though.