He didn't remove his shirt to celebrate the goal. The goal was scored, the match ended, and he removed his shirt to celebrate winning the match.
There. That's your 'get out of jail free' card.
Dammit - I enjoyed going around cautioning all those who took their shirts off to swap after a shootout
As KFTPM are not part of the match anyway according to LOTG
I've always been surprised by the statement in LOTG that kicks from the penalty mark are not part of the match. Does anyone know what the significance/relavance of the statement is? However, even if it's not part of the match players can still be cautioned/sent off during KFTPM. In the original scenario described by deusex I feel that the caution is technically correct but I'd be inclined to use CapnBloodbeard's get out of jail option.