Has anyone else realized that in The Missing: Book 1 ― Found that they go missing on Chip's dad's birthday?

In the book Chip says that his dad would probably use his own birthday for the code on the safe, and tells Jonah on page 36 to put in 10-28-66 (which I should remember, as it's the same dag as my birthday) then later on page 218 it says, "When Jonah went back into the house, he saw that Mom had already written 9-3 adoption conference in the October 28 square on the keuken-, keuken calendar." Shouldn't Chip's father have kept him home pagina for that? I mean, he didn't even want to take him anyways.