If you don't deliver a court order to a federal employee and he's wandering off to a different job he'll make sure EVERYTHING IS DELETED and overwritten with the letter A millions of times.
You may be confusing Presidential records in the White House with "federal employee".
Federal employees and contractors often receive official agency notices that they are required to save all documents related to a specific case, issue, etc. From that moment on, it becomes illegal to delete any relevant materials and you can be prosecuted for it.
You also have to acknowledge that you have or don’t have relevant documents.
Been there; done that. No sweat if you are honest. In the case of Comrade Carol Browner, she’s a lying little red bastard and always has been. Time to put her lying ass in jail for a long time.