No it would be followed up with official correspondence. Agencies don't respond to tweets if they want to cover their butts which they all do.
Most order from heads of departments [agencies] are verbal to their subordinates, actually. It is usually recorded for the record to codify it and preserve it for posterity, but it is a lawful order when stated, and to refuse it is as much insubordination in a civilian agency as it is in a military agency.
In fact, insubordination in the face of lawful direction is one case where a civil servant can be fired almost immediately and without question.