Why was Karthik given out despite Rizwan collecting ball in front of wickets?

Team India wicketkeeper-batter Dinesh Karthik was stumped out by Pakistan wicketkeeper Muhammad Rizwan on the bowling of Muhammad Nawaz in the last over despite Rizwan collecting the ball in front of wickets. The ball wasn't called a no-ball as the ball had hit Karthik's pads before reaching Rizwan. As per MCC's Law 27.3.1, Rizwan's collection of the ball was legitimate.