Describe the bug
I was messing around in my inventory when I noticed the backpack shows a tiny yellowish plus sign when I hovered near it (it was in my inventory, not my back in the curios slots). I thought perhaps I could put stuff in it by dropping them on the icon so I started picking and dropping a hopper on top of the backpack like a maniac to see what happens until the backpack suddenly disappeared along with everything in it. I thought it somehow went into the hopper so I placed the hopper on the ground and opened it and nothing was there. Checked my back slot and it wasn't there. It just disappeared :|
It was a diamond backpack, I tried to reproduce the bug with a normal backpack but it didn't work. Not sure if it's this mod or some other mod that took my backpack.

To Reproduce
Steps to reproduce the behavior:

1. Put backpack in your inventory (open inventory NOT backpack)
2. Pick a random vanilla hopper with cursor
3. ERRATICALLY left-click on the backpack, this will keep picking up each item with every click, so you'll pick backpack then drop/pick-up hopper then backpack... etc.

Expected behavior
Backpack goes poof.

Versions
Mod version: 3.17.10.621
Forge version: 40.1.0
Minecraft version: 1.18.2

My apologies, found it my storage. I guess I accidentally shift-clicked and that's how it 'disappeared' :|