Visible crew/equipment: After Arthur coerces Carrie into inviting quite a few others to their dinner she reminds him of his inside voice, then, when Arthur walks away to get the gherkins in aisle 4, there are multiple visible T-marks taped to the floor behind Carrie. (00:07:05)
Visible crew/equipment: When Arthur is talking about the store clerk hiding yam's out the back, there is an orange marker on the floor between the two men. (00:14:20)
Visible crew/equipment: When the store clerk walks off from talking to Arthur an orange T marker is visible where he was stood. (00:14:50)
Visible crew/equipment: Doug calls the phone number of the mystery guy, and when mystery guy answers his cell just a few feet away from Doug, two green tape marks are visible on the floor near Doug's feet. (00:16:30)
Visible crew/equipment: While Doug, Carrie, and Arthur are on the checkout line, Doug notices the mystery guy on another line, and two tape marks (an orange and a green) are visible on the floor near Doug's shopping cart. (00:20:20)
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.