Some Creations Have Disappeared from Creative World

Today, when I opened my Creative World, several structures I had made were completely gone and the terrain had reset to original conditions. I spawned exactly where I left  off yesterday. Oddly, one of the structures which disappeared I had just completed. The other I built weeks ago. The remaining structures were built in between with minor tweaks while doing new work. As far as I can tell, the remaining structures are complete.

After saving/quitting yesterday, I updated my BIOS. After the update I did have to enable the Compatibility Support Module in the BIOS so that the boot drive could be found. I did not make any other changes to the system. It appears that all my files are intact.

I make fun worlds to share with my kids who live in another state. I had just finished this creation and told them about how much fun we were going to have. Please help me restore my creations!