Describe the bug
I am playing in the Magical Mischief Tour modpack, ver 1.0.2
I had a backpack (fox skin) equipped in the back bauble slot, and a chestplate equipped in the standard chest slot. When I was looking inside a different backpack (bat skin), I accidentally pressed the "equip" button in the GUI. The backpack vanished, wasn't in my back bauble slot, any other bauble slot, armor slot, or even cosmetic armor slot. It didn't drop, either, just completely ceased to exist.

To Reproduce
Steps to reproduce the behavior:

1. Equip backpack to back bauble slot and chest armor to chest armor slot
2. Put items in different backpack
3. Open backpack using hotkey bar
4. Click "equip" button

Expected behavior
I expected the equip button to do nothing, or switch places with my equipped backpack/chest plate, or go into my inventory.

Required informations (please complete the following information):

• Mod version: 1.16.5-5.4.4.jar
• Mod Loader: Forge

Additional context
This has only occurred once, I don't know what factors may have affected it.

Same Issue here, if you put a second backend in the slot manually you can use the backpack, but it's pretty broken.

Try updating mod to 1.16.5-5.4.7