I found that holding shift and right clicking when my inventory is NOT full but when the furnace has items in it causes the clicked item to vanish.
To reproduce:
Furnace has input, fuel and output slots.
Iron Ore in input, output and fuel empty.
Gold Ore in inventory, Shift + Right Click
Gold Ore disappears.
I am still getting this in Windows, snapshot 15w38b.
Website seems a little weird. I cannot select any issue type other than "Bug".
I found that holding shift and right clicking when my inventory is NOT full but when the furnace has items in it causes the clicked item to vanish.
To reproduce:
Furnace has input, fuel and output slots.
Iron Ore in input, output and fuel empty.
Gold Ore in inventory, Shift + Right Click
Gold Ore disappears.