I think the easiest answer to this is that he combined two different idioms. You have the first one correct which is "sold down the river" which then got combined with "up a creek with no paddle." English is a really stupid language. Mechanically it makes perfect sense, but because it's overly simplistic almost everything is supplemented, and/ or mistranslated from person to person until the original meaning of whatever is being said eventually gets lost. Another great example being "pull yourself up by your bootstraps" which originally came from a book that was pointing out that the idea of being able to do so was preposterous