officiating. The blowing of the whistle is not what causes the ball to be come dead. What causes the ball to become dead is that something in the action of the play causes the ball to become dead, in this case a forward pass hit the ground. At the moment the ball hit the ground the ball was dead, regardless of if a whistle blew or not. The whistle is simply a tool used to signify if the play is dead. If you pay close attention, there are occasions in football where no whistle will be blown but the play ends and everybody returns to their huddle and the game goes on.
On this play there were at least 2 officials who should have known that the ball was dead when it hit the ground. The C and the linesman on the top of the screen (not sure if he was H of LJ). They both should have been able to see that a forward pass was thrown and that it hit the ground. One of them not sounding their whistle was an egregious mistake in my opinion.