Bill Belichick is usually a step ahead of NFL coaches, but in this instance it appears he had a leg up on NFL officials as well.
On the deciding play Seattle's 13-10 win over Detroit, Seahawks safety Kam Chancellor forced a Lions fumble at the goal line, and teammate K.J. Wright punched the bouncing ball out of the back of the end zone. The officials ruled the play a touchback, and Seattle took over at the 20-yard line and ran the clock out.
The referees messed up.
Batting a live ball out of bounds is illegal.