Trying to be as unbiased as possible I would say that yes he was down, however I'm not sure it was enough to overturn the initial call.
That, however, does not compare at all to the calls made that gave missouri their field goal: First the hands to the face, the horsecollar, the obvious holding not called, and then the receiver who was out of bounds.
...Wow, the big XII should give those refs a talking to.
Missouri could have put in another 10,000 seats with all the money the boosters gave those refs.