corupted file. More likely the cards fault than the camera. I would not worry about it unless it starts to happen and with other cards as well. Cards go funky slowly and sometimes the write simply gets scrambled by the camera or some kind of mishandling.
I've seen it on several of my Canon and Nikon bodies both ... usually about every 20,000th shot or so (used to shoot sports professionally - so that is two weekends
But I have to say ... at first glance I did not notice any flaw ... I just thought ... great "artsy" shot!