There Is No Other Way - S2-E16
Continuity mistake: In "Thank You So Much" Valentine's day was on a Saturday or Sunday. In this episode, They are showing Bree marking her chores off a calendar for February and March 2006. The calendar matches the real calendar and Valentine's day was a Tuesday this year. The calendar doesn't match their previous episode. And they do state that "today is Valentine's day." not that they are celebrating it on the weekend.
There Is No Other Way - S2-E16
Continuity mistake: When Susan reveals her feelings in the operating room, the face mask Dr Ron is wearing covers his nose and mouth in one shot, then not his nose in the next, then his nose and mouth again in the next. (00:38:30)
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.