One instance of mine happened about a month ago, I notified Irish that I had golden eagle boots and they poofed from my inventory or Auction House..

My second instance happened in the caves today when I tried to use my catcher of souls on the Dragon Boss in the Skrag Cave it disappeared and did not put the effect over the dragon (we died and I didn't get it back either) Now I dont have it in my inventory, even after refreshing, and I cannot complete the quest "Freed Spirit" (lvl 10 quest).