If the users local profile wasn't being backed up, one would certainly think there would be a file server to keep a users important files. However, when Outlook archive files are created the default location is in the local users profile. A user would have to manually drag the .pst files to the server for safe keeping.
Hopefully more information will leak out or be released as to what happened.
No one can explained what was being backed upped and how. .PST files are stored in the main My Documents folder now where everything typically is located. You backup your My Document folder, you back up Outlook. But my main point was, “If the backup existed for three months on tapes, why weren’t they restored the next day or so?” That is why you back up.