Really sloppy / lazy. The arm was down almost before the ball was struck. Had he kept it raised he could have simply pointed to it with the other hand to explain why no goal was being awarded.
Did the goal-keeper touch it? I don't know and neither does the referee because he made little or no effort to get closer to the incident.
I know that some of the laws of the game are a bit obscure and little known but part of the basic role of a referee is to know them and to know what to do when - once in a blue moon - such incidences occur.
How can we legitimately complain when players, managers, pundits, etc. do not know the laws ..........?