I had the same thing happen back when i was trying to lead brutes to the henge. Enemy's can not leave the district from which they are spawned.( I feel like I have posted this before) As for the phantom, either it was me and Apollo or Cold Glider and I..(it was a while ago) actually it may have been Kenji, anyways we were on MS at the destroyed bridge and a Phantom hovered over head firing at us. It was odd....I think we killed it too..