There's Something About a War - S2-E13
Continuity mistake: When Lynette and Tom are talking, Tom says "Really I got the job?" and puts down the newspaper he was just reading. In the next shot we see Lynette and you can see Tom is still holding the paper and puts it down again.
There's Something About a War - S2-E13
Continuity mistake: As the nurse is talking to Susan about the operation, the folding of the paper the nurse is holding on the clipboard changes between shots. First it is half folded over, the next shot it has been folded right over and is being held right down. After this shot it changes again and is now folded back without her moving the paper.
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.