User blog comment:Mobo85/Hot off the Presses: "Across the Second Dimension" Debuts August 5/@comment-5522044-20110731062610/@comment-181516-20110731211600

It is possible that they left stuff like this out of the book on purpose, so that way it could be shown in the movie properly and the book could at least focus on more important plot points such as Phineas and Ferb discovering Perry's secret. If you think about it, there wasn't even anything about Charlene and Heinz's relationship mentioned, such as what caused them to split up.