Restore a deleted user's documents
Sometimes shared documents belong to a user that has been deleted. In this situation, collaborators can see that the owner of the document is listed as Unknown User. If you act quickly, you can restore the deleted user and transfer ownership of the document before it is permanently deleted.
To restore documents from a deleted user:
You have up to five days after a user is deleted to restore his or her account and documents. After five days, the deleted user account and his or her documents are purged and can no longer be restored.
Once the deleted user is restored, transfer ownership of his or her documents to an active user.
As the new owner, re-share the documents with collaborators.
As the administrator, delete the user account of the original document owner. Because document ownership has now been transferred, the documents won't be permanently deleted when the original owner's account is purged.