Forum:Getting "all missions" trophy

i did the glitch where you fall through the floor in the armory and now i cant complete that mission. i was wondering, how would i get that trophy for completing all missions in t-bone junction now? i was thinking i could go to the playthrough 1 but i dont wana havta do all the missions over again. is it possible to do all the armory missions on the playthrough 1 and just do everything else on playthrough 2? would that work?