Rip Hunter was a pivotal part of Legends of Tomorrow's first season, so the fact he's been missing since the premiere has changed the show in a pretty big way. However, tonight's midseason finale provided some answers, but they probably weren't the ones any of us expected! After the Legion of Doom revealed that they need Hunter to get their hands on the Spear of Destiny, we were taken to 1967.
There, a familiar trench coat wearing character could be seen running through the streets, but the action came to a halt when it was revealed that we were on a film set for a sci-fi movie being helmed by a very different looking - and sounding - Rip Hunter. That's right, he's somehow now a filmmaker!
What led to this change isn't clear, but it's possible that the events of either the premiere or Flashpoint (maybe both) have led to him being left with no memory of who he is, hence why he's directing movies based on his old life. How that relates the the Spear of Destiny and Barry Allen's message from the future isn't clear of course, but we'll hopefully get some answers when Legends of Tomorrow returns!