Actions that constitute defensive pass interference include but are not limited to:
(a) Contact by a defender who is not playing the ball and such contact restricts the receiver’s opportunity to make the catch.
(b) Playing through the back of a receiver in an attempt to make a play on the ball.
(c) Grabbing a receiver’s arm(s) in such a manner that restricts his opportunity to catch a pass.
(d) Extending an arm across the body of a receiver thus restricting his ability to catch a pass, regardless of whether the defender is playing the ball.
(e) Cutting off the path of a receiver by making contact with him without playing the ball.
(f) Hooking a receiver in an attempt to get to the ball in such a manner that it causes the receiver’s body to turn prior to the ball arriving.
The only one that is even applicable is a) and that's disputable.
The ball hit the defender in the back while he was running after the receiver. He wasn't even face guarding.
There was no way that was pass interference.