There are no automatic backups - the only way to get your project into the steam cloud/workshop is if you tell it to upload there.
That is due to the fact that MV-projects are too big for the steam cloud - we got a lot of bad experience when that feature was automatic on Ace (most people finally disabled steam cloud for Ace) and as such it was not set to automatic when MV was developed.
If you don't have any external backup and can't undelete the data on your computer, then your project is probably lost.
There is a reason why we always tell everyone to make backups...