"The Missing Coach" was intended to be the fifteenth episode of Series 2 of Thomas the Tank Engine; it involved twins Donald and Douglas swapping their tenders in order to trick and fool Sir Topham Hatt . Halfway through filming in 1986, it was decided that the plot would be too complex for young children to understand, so the episode was scrapped and replaced with "Thomas, Percy and the Coal"/"Double Trouble".
David Mitton (writer/producer/director of the show) mentioned in a 2008 interview, (shortly before his death), that he still possessed all the original footage filmed for the episode; although, where the masters are today is entirely unknown.
7 screenshots that have appeared in various books/merchandise over the years are the only publicly available content from the episode.
Many YouTubers have reconstructed the episode, either using the existing screenshots, using model trains or toys, or using Trainz Simulator. The narration is either provided by the user, or one of the pre-existing audiobooks.