Perhaps ? Joe and Mike has talked to many people about this investigation and that the evidence is protected in many hands and many places that even Obama’s people can’t thwart it...... as in ? don’t put all your eggs in one basket... protect, protect, protect the evidence.
I expect the evidence and proof are locked up tight in a safe located in the evidence room, and possibly Arpaio and Zullo may even have stored the very critical and unique documents that are in a safe that only they know where in a secure location. And no doubt copies have been made.