Are you referring to the Award of Innovative People 2013?It was a while ago but official media refered it as 歼31 when giving award to the engineers.
Here is the AVIC news report
Here is the CCTV broadcast of the ceremony November 2014,
In both reports, Sun Cong was awarded for the work of J-15. There was nothing about FC-31, let alone the designation 歼31.
Then two months later in 2015, websites began to insert 歼31 into the event.
CCTV-1 and AVIC outlets are official although some times they make mistakes. The rest are no more than ordinate fans.