I can only find references to "it being reported in the newspaper". Cape Girardeau Argus does cover the 1863 period just barely, The Eagle doesn't. Too bad no one has indexed the Argus yet.

For those interested in Lincolns letter it is here:
http://books.google.com/books?id=9rK4JF52rugC&pg=PA6&lpg=PA6&dq=Nathaniel+Watkins+Jackson+Missouri&source=bl&ots=l6GRzUVA0R&sig=25P6D_Zog7SslrOpGZsFG_Quo9Y&hl=en&ei=A6TQTqHyEJSFtgeMrOytDQ&sa=X&oi=book_result&ct=result&resnum=7&sqi=2&ved=0CEoQ6AEwBg#v=onepage&q=Nathaniel%20Watkins%20Jackson%20Missouri&f=false

John R.