UPDATE:
EARLIER: It looks like
In our tests, as long as you have the URL for a document you can still access it. It appears that the main menu is just empty for users. We are also able to access our documents using the Google Drive smartphone app.
Those are great signs. It's likely that your documents haven't been deleted, but have temporarily disappeared from the desktop version of Google Drive.
The Google Apps status page still lists Google Drive as "orange," which confirms it is experiencing a service disruption.