A few clarifications might help us unravel the mystery. You refer to "enlistment papers," and then to "the card." What is your source for this/these document(s), and what are their nature? Are they original, are they transcriptions, are they xerox's that maybe were corrupted in the copying process, are they notes taken by a cousin and forwarded to you...? While you state the name does not appear in the 1860 census, neither does it appear in the 1870 census. What is the name of his wife? His children? Did they spell their last name in a different way than the subject in question? Was he of foreign extraction? Many who joined regiments in St. Louis were of German heritage. There was also a significant Bohemian presence in northeast Missouri, and French presence along the Mississippi. Perhaps his name has been Americanized and it appears one way in your documents, and another way in the muster rolls on file at the Missouri State Archives. Are you sure of the order of his name--Mark/Joseph/Fortune? And spelling? Mark, Marc, Markus, Marcus, Marck, Marx, Marek; Fortune, Forshun, Forcheen, Forsheen, Forshey, Fortun, Fortuni.... Name spellings back then often varied from document to document depending upon the accent of the speaker, and/or how it sounded phonetically to the person doing the writing and/or the level of literacy of the person doing the writing.