Why stop the quick throw-in?

Outside of his 22, Gordon D'Arcy of Ireland kicks the ball high downfield towards the touch-line on his right. The ball goes directly into touch where Lee Byrne of Wales catches the ball. Byrne then runs up in touch towards the place where D'Arcy kicked the ball. He throws in quickly. The referee stops him and orders a scrum to Red (Wales).

Why did he stop the quick throw-in?

It was the same ball that D'Arcy had kicked. Only Byrne had handled it and Byrne threw it in?

Law 19.2 QUICK THROW-IN
(b) For a quick throw-in, the player may be anywhere outside the field of play between the place where the ball went into touch and the player’s goal line.

Byrne was not at or behind the place where the ball went out when he threw in quickly. He was at the wrong place.

The referee was actually kind.

19.6 HOW THE THROW-IN IS TAKEN
The player taking the throw-in must stand at the correct place. The player must not step into the field of play when the ball is thrown. The ball must be thrown straight, so that it travels at least 5 metres along the line of touch before it first touches the ground or touches or is touched by a player.

19.7 INCORRECT THROW-IN
(a) If the throw-in at a line-out is incorrect, the opposing team has the choice of throwing in at a line-out or a scrum on the 15-metre line. If they choose the throw-in to the line-out and it is again incorrect, a scrum is formed. The team that took the first throw-in throws in the ball.

The throw-in was not taken at the correct place. It was therefore an incorrect throw-in. The referee could have offered Ireland the choice of a scrum or a line-out.