Thomas & Friends: Sodor's Legend of the Lost Treasure: The Movie (2015) on Netflix

Plot summary

Thomas beats Bertie the Bus in a race, and Bertie lets slip that a new branch line is going up. Annie and Clarabel fret that Thomas might lose his own line. The next morning a prank on Gordon ends in a derailment, and Sir Topham Hatt packs Thomas off to help build the new branch line while a new engine, Ryan, takes over his duties. On the site the ground gives way under the track, and Thomas drops into a cavern and finds a pirate ship. Sir Topham Hatt takes the report as an excuse, and Rocky the crane gets the credit for the find. Thomas meets Sailor John, who says he is after treasure but keeps the details to himself. Skiff, John's boat, has wheels that let him run on rails.