If they were destroyed when surrendered after Hilary’s departure, that would be in accordance with security procedures. They should have been backed up securely of course before hand.
IIRC, Orange book specs require all decommissioned HD and other magnetic media to be destroyed. This has been around for a very long time.
Yes, private business does the same thing to certain computer HDs, but the information is always backed up first. So it’s available somewhere. :-)