This issue happened in Cataclysm Classic on the character I’m posting from.
After killing Ragnaros this week on Thursday, I autolooted the items out of the cache, leaving only the Seething Cinder’s and Eternal Embers in the cache.
I moved off of the box and the cache had immediately disappeared without me looting the quest items.
Is it possible to have these items restored? It delays all of the raids Dragonwrath staves by a week because of this bug.