I completed building several houses in my world last night. I know it saved because the last house I was working on is still there but the progress in my other houses aren't there.
I discovered this when I tried to log into my world using another xbox we had in the house. When I loaded the game, it said it needed to activate the resource pack and download it. It instantly was messed up once I loaded it and has yet to fixed itself since then. I tried loading another one to see if it was ok but was unable to use that one as well.
One house is completely gone, another is missing 2/3 of it, another has a couple things left inside but most of the progress is gone.
Your using Bedrock edition, and this tracker is for the Java edition, maybe try the Bedrock issue tracker (its sometimes called MCPE, as bedrock stems from the Pocket Edition).