Continuity mistake: When Bree, Susan and Lynette are scrubbing the road, a red sports car zooms past them. Lynette stands, hurls abuse and throws her scrubbing brush at the car which can be seen bouncing off the car and down the road. She then kneels down and continues to scrub with the brush.
Continuity mistake: As Susan tries to get the dog to help the second time you can see the towel Susan tried to use to get the dog to help her. The shot then shows Susan and the towel has disappeared. After a quick shot of the dog it cuts back to Susan and the towel has reappeared.
Answer: Kayla was sent away in episode 16 (The Gun Song) in season 4, after falsely accusing Lynette of child abuse. She now lives with her grandparents - probably Nora's parents.
I'm curious why we never see her again, why she never talked about, and why Tom never mentions visiting her.