You've nailed it. The cord is there, but the motion blur makes it hard to see. If you look at some of the Marines in the audience, you'll see other examples of motion blur: One guy's elbow is moving and another's hands are a blur. Sorry, folks; but no fauxtography here.
The giveaway is the dark-haired soldier who is standing against in far wall in line with the "blur". His face is intact. If the cord had been Photoshopped out, his face would have to be an inserted copy of another face in the crowd.