I was playing on an LAN game. The Minecraft world was created on a previous date. We just logged in today for the first time in a while. We had lost the previous inventory, so we had to create new everything to start back up again. I logged out of the LAN game for a brief time period. When I logged back in, after 5 minutes, I got my old inventory back and lost everything I had just mined!
Thank you for your report!
We're actually already tracking this issue at MCPE-55815, so we will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature, to see if the issue has already been mentioned.
Quick Links:
📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki