Enchantment disappearing on item

I made an item that opens a GUI with a bunch of buttons. If you click on one of the buttons it opens another gui with a button and one input slot. I have a procedure on that button to add an enchantment on the item in that one input slot. When I do this it works and I move the tool back into my inventory... but when I open a chest that enchantment disappears on the item and I can't figure out why.