Lost Non Stop Data Backup After Windows XP System Restore

I have Windows XP Pro. I am running Acronis True Image Home 11. I am using the nonstop backup. The nonstop backup data is stored on a external USB drive.

The external USB drive is included as a drive that is part of the Windows XP system restore function.

A few days ago all of my nonstop backup history was gone. I did run a system restore about the time my data disapeared. I also had an employee leave suddently and she may have erased the backup to cover her tracks.

Could a Windows system restore cause me to lose the data?

If the data was deleted by someone, would there be any log that would confirm that?

Thanks