i've put a stack of twenty entropy orbs to turn them into legendary ones thinking its gonna return the 19 rest in my inventory, but it doesnt, so i just lost 19 of them to get one legendary entropy orb. and just now when i wanted to transmute another one again i put another stack of 20 inside and remembered i should unstack just one, so i closed the window by clicking X while my orbs were inside the "insert item" place and then when i looked at my inventory they weren't there.
Funny thing is, knowing how buggy the game is, for a fraction of a second i thought i should have put them back in the inventory myself, but a mistake was already made.