https://www.youtube.com/watch?v=vWyCL3sdXqA&feature=youtu.be&t=10409
2:53:20 min mark
For people wondering that it could be a demo version of the Captain Hook ship featured in past KH games, it looks significantly different. While the map is clearly unfinished and doesn't perfectly resemble the ship featured in the movie, the code related to this group of assets is titled "tp". All maps in past KH games have abreviated area codes like "tt" for the Twilight Town maps or "pl" for Pride Lands.
This world consists of 11 rooms (maps, areas), as found in the code. This is not the first time S-E leaves scrapped or unused material hidden inside the KH games. Assets from a Pinocchio world were found in 358/2 Days and Toy Story character models were found in KHII. Birth By Sleep also featured nearly finished The Jungle Book maps and enemies that were likely repurposed into the Neverland world.
While this doesn't mean that Treasure Planet will be featured as a world in future KH games or KH3, it's nice to know the team considered including it in KH3D. Tetsuya Nomura also stated that the team also considered including 'Tron' and 'Fantasia 2000' worlds in this game.
Thanks to the youtube user OmegaErkz for finding this.