You aren't listening. I don't think he was part of the media, just part of the group that went with her or even somebody who entered when he saw her entering.
For instance, they take along a group of media and some "friends" (more likely donors and others who had worked on the campaign to 'earn' a few minutes with Michelle) who went along for the ride and to be part of "history", among those was a black gentleman who either had his own cell phone or was handed one and told to take a picture while the media were taking pictures of Michelle.
They held the line so the shot to Michelle was clear and had the guy go on up to take "his" picture on the cell phone, the media took pictures of that moment along with a zillion others.
Part of the "mystique" is how much other people just think Obama is "cool" and they work towards this, as they did with the Iraqi military personnel and the cameras they handed to them. If somebody didn't step up to take the picture (doubtful because it is clear that they held the line for the photos), they would have staged it.