This is specialized knowledge. Perhaps a few IT guys were aware of this contract and this software; however it runs on the servers, not on client desktops. A paper pusher would not know what happens to the email, and where it is stored. Many think that if they delete an email it gets deleted. That's not always so. MS Exchange is a complex system, and one can insert transport agents into many places of that system. Most people do not know what servers they connect to, and what are the backup procedures on those, and where offline backups are stored, and for how long. Managers of high rank are sometimes sufficiently arrogant to not ask the IT people about such details. After all, in order to ask a correct question you must know most of the answer already. People who are trained on simplistic "Press DEL and the email is gone" cannot even imagine that the email is not really gone.
Crash of a client's PC has no effect on the data. MS Exchange stores emails in MS SQL Server databases; many such databases can exist, and they can be all synchronized (replicated) for many reasons. For example, you cannot have 100,000 employees, who reside all over the planet, connect to one server. So there are multiple edge transport servers, hub transport servers, client access servers and mailbox servers. Just look here.
If they were running exchange, those emails were backed up, and are on media or a drive array somewhere. They could probably be fully restored within minutes.
I’ve worked with places that have crazy mailbox size quotas, which requires the users to not keep emails very long, or save them to .pst files, but even THEN, those emails would still be backed up from Exchange most likely before deletion/user archival. The user’s .pst files are indeed often kept on the user’s computers, but are usually saved within a redirected/networked folder which resides on a file server, that’s ALSO backed up. Even IF the .pst file IS on the user’s local drive and it “crashed”, most of the time data can be recovered from a failed drive.
For those emails to not be recoverable, they would need to have one of the most pathetically sloppy IT departments in the history of the government, terrible business practices, and some of the worst luck I’ve ever heard of. It simply didn’t happen the way we’re being told.