Ok, so in an effort to get power armor and finish the Cass quest at the same time, I go to the Silver Rush and leave Cass and Rex outside. I wanted to clear out the Silver Rush before turning in the evidence and making an oath not to harm them. So, I clean out the Silver Rush (after 4 tries), walk out of the building and Rex is the only companion there. Cass has vanished. I went to the Mojave Outpost and she isn't there. Anybody know why or where she runs off to?