Complex sentence: Swindon is only referring to the 2015a and 2015b sentences which were edited in and out but the 2012 sentence was still there; it hadn't disappeared and he would have seen this if he had taken the time to read the page properly.
Split into simpler sentences: Swindon is only referring to the 2015a and 2015b sentences which were edited in and out. The 2012 sentence was still there; it hadn't disappeared and he simply had to read the page properly.