Continuity mistake: When Doug and Carrie are arguing over Arthur having a house, the head on Doug's beer keeps changing size. (00:02:00)
Revealing mistake: Both times when you see an overview of the bridge, it's the same clip being used. (00:07:10)
Visible crew/equipment: The second time Doug pulls up at the toll booth, stage lights and equipment are reflected in the car's paintwork. (00:07:20)
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.