Absolutely. Rules and laws are there to be interpreted. A player will get booked for lifting shirt because of spectator incitement. But when you take the facts into account, that this was a personal message from the lad in regards to his passed mother, the referee is in the position to interpret if the rule is in place for this situation. He could have come to the conclusion that that is not what the rules intend it to be for, and thus, not book the player.