Other mistake: Bree is drinking wine with Karl, but before in other episodes and season and episodes and seasons after, she sternly says she does not drink because she was an alcoholic.
Nice Is Different Than Good - S6-E1
Continuity mistake: At the end of season 5, Lynette finds out she's about 6 weeks pregnant. At the end of the same episode, they do a "Two Months Later." In Season 6, Episode 1, Tom says after an argument with Lynette "Only 8 and a half more months." Lynette should be in her second trimester by then, with at most 6 months to go.
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.
Audio problem: During the dinner scene at the Scavo's home, Lynette tells Irina that her son Preston is "blinded by a piece of Eurotrash who would sell her own mother for a pair of designer jeans." When the camera changes to behind Lynette in the next shot, she can be saying the words "designer jeans" again, but this time with no sound.
Other mistake: When Bree goes to talk to Eddie Orlofsky's mother, she introduces herself as "Bree Hodge." However, she proceeds to talk about how Eddie likes her daughter Danielle, but her daughter "doesn't return his feelings, she spends most of her time with the other cheerleaders." In the scene before, Eddie had also mentioned that he liked a girl "from school." The problem is at the time that Danielle was in high school, Bree was not "Bree Hodge", but "Bree Van de Kamp." She hadn't even met Orson Hodge then. (00:19:10)
Other mistake: Throughout the sixth season Eddie Orlofsky attends school with Porter Scavo, and Danny Bolen, witch means they must be close in age. However, in season 6 episode 20, it is revealed that Eddie was in high school the same time as Danielle. This does not make sense due to the fact that while Danielle was in high school, Porter and Preston were about 10.
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.