Lincoln was exerting great secrecy.
You said: And this is Lincoln's super secret plan for invading Charleston? The one he informed Governor Pickens on?
Then explain this:
Order of the President of the United States to the Commandant, Navy Yard, New York.
The fitting out of the USS Powhatan
Executive Mansion, April 1, 1861
Sir: You will fit out the Powhatan without delay. Lieutenant Porter will relieve Captain Mercer in command of her. She is bound on secret service, and you will under no circumstances communicate to the Navy Department the fact that she is fitting out.
Abraham Lincoln
http://query.nytimes.com/gst/abstract.html?res=9404E4D9153CE433A25753C1A9679C94669ED7CF
Anderson said he would defend himself against acts of aggression.