The MSD2D site at http://www.msd2d.com has a few documented SharePoint Technology Tips that provide file-restore solutions through the Microsoft SQL Server SharePoint content databases. Dennis Moxley provides one of these tips in "Item Level Restore in a Document Library" (http://msd2d.com/content/tip_viewitem_03noauth.aspx?id=18b3b9d7-bcd4-465f-9bd7-8ece0bd1e9bc§ion=sharepoint), which describes restoring a document through a SQL Server backup. Using SQL Server backup can be a more effective approach for backing up and restoring portal content as it gives you more flexibility in the management of the content directly from the databases. (You’ll have to register with MSD2D to see this and other tips on the MSD2D site.)
In this approach, Moxley explains how to identify the location of files within the Doc database table by using an SQL query that you run against the backed-up SharePoint site database. Then he tells you how to build a new query that adds the content back to a production content database. You can append the query results to the production site database's Doc table by using SQL Server Enterprise Manager's Import Data feature. As Moxley points out, you'll need to create additional configurations to get a SharePoint document-library list view to recognize the file restore.
You can also find a similar approach on the MSD2D site in Carlos Montilla and Jim Beam’s "File Level Restore" tip (http://msd2d.com/content/tip_viewitem_03.aspx?section=sharepoint&category=administration&id=6fbc9145-cc08-4a5b-a7d7-14b37e014672). This is an automated approach to content recovery that gives you precise control of the backup and restore process. Montilla and Beam's approach provides a holding table with triggers and stored procedures to do what Moxley suggests in the first tip. These are effective approaches to file restores; however, they map directly to the database schema of the SharePoint site, which Microsoft could alter in a future update to SharePoint Portal Server.