So I was moving from an old world to a new one and swapped from Forge to Fabric & I wanted to give myself a backpack that I previously had. When I tried to give myself the backpack from creative it disappeared multiple times, when I would pick up a dropped item it would replace the backpack and the backpack would be gone. So then I tried to just give myself the items to craft the backpack, but the tanks I had given myself also disappeared. I tried looking up the crafting recipes in REI and no recipes appeared.
I'm playing on version 1.18.2-7.1.12 Fabric with all the required dependencies.

Check your installation, if you play on server check if mod is installed on server etc.