I just had it happen as well, except now whenever I re-enter the mission, I'm put at Trahearne and it says pick 2 allies. I run back up to where the allies are, and there is a wall blocking them off. So unless there is a way to restart this whole episode that I can't figure out, I cannot continue, period. Sad times if it's been a bug for so long. If I can get it to reset, I'll pick the other two....