Barry the Rescue Engine was intended to be an installment of the popular British children's book series, The Railway Series, of which the television show Thomas the Tank Engine is based on. The book was to be written by Christopher Awdry, the son of original author Rev. Wilbur Awdry.
Awdry wrote the book sometime in the 1980s, and would've introduced the titular character Barry (who who has been confirmed to be a BR Standard Class 2 Darlington Work's Engine with a 2-6-0 wheel configuration) that worked at the Sodor scrap yards. The book has been confirmed to heavily feature the owner of the railway Sir Tophamhat (otherwise known as The Fat Controller) and was likely to feature Duck, Oliver, Donald, and Douglas, four other engines that had ties to the scrap yards one way or another.
However, the company that published The Railway Series demanded to have more Thomas centric books, and refused to publish Barry's debut appearance in the series. This was likely compounded by the fact that, at the time, the television show based on the book was running strong and had catapulted Thomas into the spotlight. At the time, Britt Alcroft (producer of the television series) was under contract that she could only make episodes based on stories from the book. Therefore, it is likely the book More About Thomas the Tank Engine, a book specifically written for that reason, replaced Barry the Rescue Engine.
Sadly, Barry hasn't seen the light of day since his debut book got cancelled, outside of a few fan made projects made using the Trainz engine (no pun intended). Considering the highly merchandised based aspect of The Railway Series and Thomas the Tank Engine at this point, there is still a chance Barry could make his way into the official series. This is however very unlikely due to the introduction of All Engines Go! in 2021.