The best solution is (assuming you do regular backups of you Spira instance) is to do the following:
- Install Spira onto another computer and restore a backup of your database onto that server.
- Use the Spira Project Backup and Migration Tool to download the missing project from that server into a .PRJ file.
- Now restore the project onto your live server using this .PRJ file.
What is the Spira Project Backup and Migration Tool?
This a utility provided by Inflectra that lets you backup, restore and transfer single projects between Spira installations: