This happens to receivers all the time, the bump was minimal, yeah maybe should have been a PI but 90%+ of NFL receivers still catch it. You can find thousands of plays where a guy catches the ball and there is pass interference. It was terrible technique by Thornton, that's why he dropped it, not because of a minor little bump you need to strain to see.
I watched this play probably 30 times. The defender is actually slightly in front of TT, the ONLY reason TT moves at all is because he jumps for a ball he has no need to jump for, otherwise the contact would have never moved him. He never reaches out with his arms so the ball hits him in the chest as he tries to catch it cradling it to his chest. It's just poor technique all the way around.