Silas' Sphere of Transmutation
156631

The item keeps getting "sold" automatically to vendors and doesn't appear on the buyback screen. It has to be restored via ticket. The materials for this are expensive and annoying to farm and you should only have to make one of it without worrying about it getting destroyed every time you talk to a vendor.

Added in internal build

My experience is not that the original item is sold, just the four it has turned into, like the potion of endless curing.