As I have told you, system restore does not back up things such as "my documents" because you don't want these to be affected by restoring. You don't want your newer documents to be removed or put out of date because of a system restore. The point of a system restore is to get windows booting and working as it was at the time of restore point creation and documents are unlikely to be causing the OS problems. System restore is there to protect your registry etc.
Most people will have their important documents on their C: as that is the default location. The people who move them to a drive other than the boot drive to be able to, for example, reinstall windows without losing data, are a minority.
Still, they probably should have booted into a linux liveCD to see what was on the drive they were overwriting first. That's something I would have done, but I expect they asked your permission to overwrite it and exptected you to know what was on it. That is the lazy approach, it assume's the user's not a total newbie and knows what's where on their hard drives, but it absolves them of responsibility.
In the end, we've all gone through catastrophic data loss and it teaches us to follow best practices around data backup in the future.
Ahh well. Win some lose some.