Prophet must have dropped his scar as he was swept away from Nomad mid game, The Moac was basically a pick up that he rigged so he could fire it.
Just before you jump down and finally meet prophet again, if you look across the the far hill you will see the MOAC sitting in front of the ruined shack on hilltop, then you go cutscene.
So far I havn't seen a metion of any kind of Ice for Crysis 2, and was wondering if this will be in the story line, but I will settle for being able to rip some kind of alien weapons.
