After upgrading Lightroom today, I wasn't able to sync the changes I made in the mobile version and the cloud deleted all of them. Can you restore these files? I was nearly done with editing and now everything is gone!? Thanks in advanced
If you have deleted all data by going in Desktop Lightroom Preferences, then there's no way to get it back.
The only thing can be done is to re-sync your Desktop Lightroom collection again to the Lightroom Mobile.