David, I do not agree that Lincoln had no idea that Charleston was supplying Sumter because Fox had visited the fort prior to April 9. It was because of Fox's visit to Sumter the mail was cut off on April 9. I have this right now.

War of the Rebellion: Serial 001 Page 0292 OPERATIONS IN CHARLESTON HARBOR, S. C. Chapter I.
STATE OF SOUTH CAROLINA,

Headquarters, April 9, 1861.

To the PRESIDENT OF THE CONFEDERATE STATES:
MY DEAR SIR: I send by the bearer important dispatches to the Secretary of War, and beg to call your immediate attention to them. The bearer is Colonel Hayne, an aide of mine, and will return immediately to me. If you have anything particular to General Beauregard or myself, you can trust it to him, and he will bring it back immediately. Since I inclosed the dispatch to the Secretary of War Major Anderson has written a polite note to General Beauregard, requesting that the letters taken from the mail might be returned, as he had been notified that his mails would be stopped entirely. The general returned for answer that the private letters had been sent to their destination, but the official letters were sent to the Confederate Government, because rumors, well established, indicated that Mr. Fox had violated his faith to me in visiting the fort, under the guarantee of Captain Hartstene, who went with him. The pledge was that he visited Major Anderson by authority, for pacific purposes entirely. You see that the present scheme for supplying the fort is Mr. Fox's. It is thought that the attempt will be made to-night, and we have doubled our steamboats on the harbor and bar.
Since I wrote to the War Department we have increased the forces on Morris Island to two thousand one hundred men, and ten companies of fine men arrive to-night, in the next train, of eight hundred men, and two more regiments arrive to-morrow. We hope to have about six thousand men there on the harbor batteries and posts. I trust we are ready, and if they come we will give them a cordial reception, such as will ring through this country, I think. I hope we are not mistaken; but, at any rate, we will try and do our duty.
With great esteem, yours, very truly,

F. W. PICKENS.

Also Genl Totten had this letter--

FORT SUMTER, S. C., April 8, 1861.
General JOSEPH G. TOTTEN,
Chief Engineer U. S. Army, Washington, D. C.:
GENERAL: The increased activity and vigilance of the investing force, as reported yesterday, still continues. Three large traverses are nearly completed on the front, from battery Numbers 3 to 5, on Morris Island, and traverses are also being erected in the interior of battery Numbers 5. Additions of sand bags are being made to the covering of the magazine, between Nos. 2 and 3, and to the left flank of Numbers 1, where I think they are constructing a service magazine.

I am busily at work constructing splinter-proof shelters on the terreplein. I obtain timber by taking the gun carriages to pieces, and form the covering of the 2-inch iron pieces for embrasures, as seen below. The plates are spiked on, so as to be securely retained in their places, even if struck by a shell, which I am confident it will turn.
Our supplies are entirely cut off from the city, and those on hand are very limited.

The besieging forces worked all day yesterday, whenever the intervals between the showers of rain would allow.
Very respectfully, your obedient servant,

J. G. FOSTER,
Captain, Engineers.
P. S. - I received yesterday a letter from the Secretary of War to Major Anderson, which, by mistake, had been enveloped to me. I handed it to Major Anderson without reading.

Respectfully, & c.,
J. G. FOSTER,
Captain, Engineers.

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That indicates to me the facts was well known throughout the chain of command, perhaps all the way to Lincoln.