Missing Chimeral Inscribed Ultimatum

I also have the same problem and I can't get the key now, is there any help with this?

Yes, same here. Exactly the same - upon picking up it is gone. I was almost convinced I disenchanted it to vendor by mistake (that should not be possible). Fellow player provided me with a normal non-quest ultimatum, which works, but because of the level difference it was not manageable for me to completed and it is one-use only. Upon death it is gone. Therefor re-triggering the quest with non-quest ultimatum is quite costly (1ex each try). We need the quest item back :)

same!!!
Back the quest item!

+1

Same to me today.
Full inventory upon killing the boss, the Ultimatum was on the ground, and instead of refusing to pick it up it was just deleted instantly.
Can not complete the quest, and doing the boss again does not drop a new one.