0. ALWAYS PROVIDE INFORMATION ABOUT MODLOADER (Fabric / Forge) AND MOD VERSION (For Example 1.19.2-8.2.10)
   version 1.21 fabric

1. Describe the bug.
   My backpack disappeared when I returned to my world after a long time.

2. Write down the steps to reproduce the bug.
   I don't know.

3. What is the expected behavior?
   I want to be able to get my backpack back.

4. Screenshots (if applicable).

Not possible for me to do anything with this report, everything could have happened, maybe you've updated some mods and something bugged out or added mod that provides back slot/removed it