I was farming the Dissector’s Staff of Mutation and looted it but either moved or something before not realizing there is a yes or no dialogue option to continue looting. The staff disappeared but i got the achievement (my only treasure so far). I have now tried to farm it again 3 different times. After someone else swiping it from right under me for the 3rd time, I recall something I read on about peoples experiences, one of them citing that if you have looted it, you cant see it again. I think I am in a limbo state where I dont have the staff but also cannot see it.