While ninjaing on such a level really hasn't happened to me (now i've gone and jinxed myself!), it seems that once you open a ticket and name the person who took it and who should've won it via roll, as long as loot rules were established beforehand that does count as 'ninja looting' and said ninja will recieve a ban or punisment of some sort and the person who should've won the mammoth will actually recieve it.
A terrible event has happened. while i was doing VOA and killed koralon the Grand Black War Mammoth mount had dropped then we rolled on it. I didnt win but some other guy did but then the Raid Leader ninjaed it. Alot of people were pissed off and started to leave then the raid leader left then i left. The guy was kicked out of his guild for doing that and some peopled tickited him. Still I feel like kharma should get back on him more (Feel sad for the guy who won the role but didnt get it).