All Buildings Disappeared on Old Type World

I was building a scavenger hunt on an old type world. I had been working on it for about half an hour and then needed to turn off my phone. If was off for a minute. When I opened it back up, everything I had built was gone. I looked around and all that was left were the things in my inventory. I restarted the app to see if that would help, but nothing. It looks as if I had never done anything in the world.

I tried to recreate it by building something, using a book and quill, and then turning off my phone, but it didn't work. I also tried to attach a video but I couldn't make it small enough.