To recover a deleted records or, specifically a Private View, head to Other > Admin > Logs > Deleted records.
When you are in your Deleted records page, you will see a log of all the records that have been removed from your database.
To restore your record, search and find your record, click 'View' to make sure that it is the right one, and then click 'restore'. It will now reappear in your database.
Find your Private View (Artworks > Private Views > All) > click the 'pencil edit' icon > open Settings > Login/Expiry > empty the expiry date field, which will have been set to 1999 > Save. This will allow the Private View to be live.