If it was official business there’s a good chance there are email CC and BCC distributions that may appear on other drives within the department, as well as the original recipient, whoever it was.
If the “crashed” hard drive still exists, a forensic examination would show what caused it to crash and when.
If the drive does not exist, but every other drive in the Agency has been preserved, that would be proof of a willing effort to destroy evidence.
Either way, somebody is going to be in a lot of trouble.