Visible crew/equipment: When Doug is working at Cooper's, and goes to get the ladies beer nuts, the camera pans to the left, and a 2nd camera (which is used on the following shot of Doug) is visible on the left side of the screen.
Deconstructing Carrie - S7-E15
Visible crew/equipment: When Carrie comes into the house after being hit on by the construction guys, a shadow (boom mic) passes over the TV. (00:12:45)
Wish Boned - S7-E17
Visible crew/equipment: When Doug starts to walk over to the flight attendant, a second camera slides into the shot for a few seconds to the right of the screen. (00:12:36)
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.