How do you get an unconscious familiar back into your backpack? You can't talk with it because it's, well, unconscious... do I just have to leave it behind?
Assuming it's not dead, heal it. Then talk to it as normal to return it to the pack. If it is dead, you can dismiss your familiar, and call a new one after a year and a day has past in game time... I don't actually know what the length of a year is in Oerth though. 400 days should do the trick, if not just rest more.