My stuff disappeared!

I have a Minecraft world with my friend, and when we were mining for diamonds he decided to try a duplication glitch he saw in a video where you put your items in a chest then break the chest and exit minecraft. It worked, so he tried it again, but this time when he rejoined, all his stuff was gone instead of duplicated! I guess it's just a 'Bedrock Moment' or something.. Anyways, it would be great if this was fixed and I'd appreciate any suggestions on getting my stuff back. Otherwise, I might just use commands to get it but that feels like cheating.