My personal belief is that they are lying from A-to-Z about this, and it's a criminal coverup far exceeding anything that the Nixon gang ever contemplated. When I worked for a major corporation, my PC and unix box were backed up NIGHTLY, and I was just a peon.
To contend that high IRS (and other gov't agencies) mucky-mucks don't have strict backup requirements and that anything on them can be tragically, accidentally 'permanently lost', strains credulity and insults intelligence.
Agree about the coverup.
The big hole in their lie is that there are more than one hard drive involved, plus the servers/backup... the info IS there.