I was in my world, in the process of building a massive structure. I turned off Minecraft and returned half an hour later, but over half of my structure had disappeared. This had also happened to another one of my structures, and every many of my other structures had completely disappeared.
I feel like it's important to clarify that I had backed up my world a few days before. I don't know if there's any way to restore it back to what it was when I backed it up, but if I could get some help and support with this issue I will be extremely pleased.
Related issues
Attachments
Comments

Thank you for your report!
We're actually already tracking this issue in MC-150202, so I resolved and linked 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.
You can find your backups by going into your .minecraft
folder, and enter the backups
folder. There, you'll find all backups taken by Minecraft. Just unzip the file and put the folder inside of it into your saves
folder to restore a backup.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.