The ball was a good 5-6 yards under thrown and touched by a defender prior to the ball getting to the receiver(in this case intercepted). It can't be PI. They could of called illegal contact past 5 yards but that is rarely called these days.
BTW, Brady got away with a grounding call on that 3rd and 10 where he threw down the ball in the left flat when his receiver was on the right flat. That would of made it 4th and 18 and who knows. The calls equal out.