How about we call you silly for taking a person's opinion out of a blog post as gospel truth?
In conjunction with the loss of many of the wartime records, the paper trail for a stalled policy thins out for the last year of Lincoln’s life, but it does not disappear.
Loss of what wartime records? Literally every word Lincoln wrote or spoke for the record is available online. Add to that the Official Record of the Rebellion contains every written order or report to and from the army and I'd say that Lincoln's administration and the Civil War is one of the most carefully documented periods in our history. Certainly in the 19th century.
You can't search the internet yourself? Well Major General Benjamin Butler did say it, and it can be verified by any number of other sources. This article also proves he was in Washington at the time he said he was, Which pretty much knocks down the argument of critics to the contrary.
There is also this little gem at that link.
Throughout this period Butler was aware that Treasury Department agent Hanson Risley accompanied the president at City Point.[31] Risley, incidentally, was a central figure in the larger cotton-trading controversy that had drawn the ire of several northern congressmen against the Lincoln administration, including criticism directed at the president himself. A close associate of Seward and political boss Thurlow Weed, Risley had been involved in the granting of cotton-trading permits with the south to Lincoln's personal friends, including Leonard Swett and the brother of Ward Hill Lamon.
Loss of what wartime records? Literally every word Lincoln wrote or spoke for the record is available online.
You should solicit your answer from the New York Times Blogger who wrote it. His name appears to be Sebastian Page.
You seem to be attacking the messenger. Perhaps you should attack the message? I don't think you will have any luck there, because it appears that the claim is true.