If they are using the Ditto Drive for their backup. There is a very quick and reliable way to verify that the files have been backed up
Go into “The Works” The ditto software and Choose TOOLS from the top menu.
The first option is Read Tape Info.
Choose this and it will read the tape in the drive and give you the statistics, as well as allow you to open up each branch of the tree and see the files that have been saved.