I find this odd. In the episode "The Runaway Caboose", Caroline, nor Carrie were on.

What was odd, is I don't even think they were mentioned ??? (I missed some minutes)

Whenver Charles in not on, and someone could correct me if I'm wrong, I do think he is mentioned.

This episode was shown after the episode, where Caroline thinks of amputing her leg.

Caroline's part in a lot of episodes, is not that big. Maybe after having an episode concering her, the actress needed a break ???

Not really, this episode was a trip with Charles, Isaiah and the girls and Carl. We know where the rest of the family is, so why keep bringing it up. There were lots of episodes like this. Just because Caroline or Carrie were not mentioned, I knew that Ma was home with the child waiting for them to return.