I was trying to access my Iron Furnace but accidentally i right clicked it with a Yeta Wrench. After that the item i was smelting disappeared with the fuel inside. Probably this bug can be seen on all of the More Furnaces furnaces.

I've been aware of this issue for quite some time, I'm surprised to find there was no ticket for this from last year.

It's a bug with MoreFurnaces, which hasn't been updated in a very long time. There's nothing we can do except use a different mod, frankly.