I had "Don't bite the sun" ready up to the point of needing to get Pavarti fancy clothes. I had to wait until the next area was unlocked for this, so went about completing "Friendship's Due". When I completed the quest for Felix, no matter what I did, I could not finish without failing Pavarti's quest. I'd go to speak with Felix and wrap things up and after all the xp gains etc, I would hear the "mission failed" sound and then the pop up in the top right to say that Pavarti's quest was over. In the end, I had to just allow Felix to leave with Darlow to keep Pavarti's quest line from failing

What gives? Can I get Felix back later? Why did this happen?

It actually seems like a pretty common bug and it isn't connected to Felix's quest. Don't Bite the Sun just randomly fails because the game thinks Parvati is dead, even if she isn't or if you're playing on normal where Companions can't die.