Ok i cannot find a video of the incident but i found one pretty similar involving Sterling against City. He gets his shot off and then is clattered. So is this a penalty?
http://www.101greatgoals.com/gvideos/awful-miss-liverpools-raheem-sterling-blazes-over-from-close-range-vine-video/
Like i said. This happens a lot in a lot of games. IF you are going to give free kicks and penalties every time this happens, then it will happen a lot.
Rules say that it needs to deny a goal scoring opportunity. So if they get their shot off no. Similar if Erikson's goal had been saved by De Gea, then would we get a penalty because Valencia missed the ball but kicked Erikson in the head