Audio problem: When Gaby goes to introduce Angie to Heidi Klum at the fashion agency, Gaby goes up to Heidi and says "It's me, Gaby." When the camera angle changes to behind Gaby in the next shot, she is saying the same thing again, but no words are coming out.
Continuity mistake: When Susan and Mike are lying on the floor in the kitchen, Susan says to Mike "You can pay the loan off by yourself" and Mike has his left hand on Susan's wrist, but in the next shot, he no longer does.
Continuity mistake: When Gabrielle asks Angie if she would like to meet Heidi Klum at the modelling agency, the magazine Gabrielle is reading is open, but when she says "Sure, she's an old friend", the magazine is closed.
Audio problem: When Gaby sees Paulina Poriskova in the restaurant, she puts out her arms and says, "Give me a hug!" but her lips barely move.
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.