Didn't see the exact place in the video, but perhaps you are talking about the nozzle stiffening ring? http://www.spacex.com/news/2013/02/09/falcon-9-flight-1-

Didn't see the exact place in the video, but perhaps you are talking about the nozzle stiffening ring? http://www.spacex.com/news/2013/02/09/falcon-9-flight-1-pictures http://www.spacex.com/news/2013/02/09/falcon-9-flight-1-pict... has a still of it happening on a previous flight towards the end of the page.