Mammary Lane - S5-E5
Continuity mistake: At the beginning of the episode, the establishing shot shows a bowling alley with a sign that reads Mar Lin Do Lanes. A few minutes later, Doug welcomes Denise on behalf of the family at Bowl-O-Rama. (00:04:10)
Answer: Sara hasn't been mentioned in later episodes, and it suggested in later episodes that she never existed, and that Carrie is an only child. Kevin James stated that the producers couldn't think of an good plots to use with Sara, so they left her out.