Currently for Project restoration there are 3 possible ways for System Administrators to turn to:
1. Exporting/Importing into MS Project file: System Administrators can recover it from Sandbox Preview environment via exporting it into MS Project file then importing into the Production/Live environment. But here some info will be lost – Updates and Hours.
2. Export/Import via Kick-Start Data Importer:
(NOTE NOT INTENDED TO TRANSFER PROJECTS BUILT IN PREVIEW SANDBOX TO PRODUCTION, ONLY FOR RESTORATION OF LOST DATA)
System Administrators can do this manually via Kick-Start Data Importer, which needs to be done very carefully. See the help-site article: https://support.workfront.com/hc/en-us/articles/216607028
-Login to Sandbox Preview
-Change your email to a valid one in "My Settings"
-Go to Setup>System>Kick Starts>Export data
-Click on More options.
-Check the box for Projects (and Tasks, Issues, Hours if there are any within the deleted Project).
-Copy the Project's ID from within its URL
6. Download the Excel file> search for the Project's ID> change FALSE to TRUE in front of the preferred Project's ID (and do the same for ALL sheets by finding Project ID and marking the rows for "isNew" TRUE)>Save
5. Go to Live> Setup>System>Kick Starts > Import data > Upload the file
6. Check if the Project with the corresponding items is imported.
* Note: Here some info will not be imported – Updates and Documents.
Please see also more info on this here: https://support.workfront.com/hc/en-us/articles/217179547
3. Contacting Support: Authorized Support Contacts can contact Customer Support and initiate a restore through Workfront Customer Care.