When Darth Maul debuted in The Phantom Menace, he was immediately intriguing to Star Wars fans. He was the first new Sith Lord in a Star Wars movie since Emperor Palpatine and Darth Vader in the original trilogy. Everything about Darth Maul was intriguing, from his tattoos and horns to his double-bladed lightsaber. But Maul's most underestimated contribution to Star Wars' lore was his starship, which seemingly vanished from Star Wars lore.
A modified Star Courier vessel, the Scimitar was also known as a Sith Infiltrator. In addition to its heavy armaments for a ship of its size, the Scimitar was also equipped with a cloaking device. This was an incredibly rare piece of technology in this galaxy. Making the ship even more special was the fact that it could track another ship through hyperspace — a feat few vessels were capable of.
After the events on Naboo depicted in The Phantom Menace, Maul was believed to be dead at the hands of Obi-Wan Kenobi. Many years later, fans would learn in The Clone Wars that wasn't the case. Maul survived and would continue to menace the galaxy until Obi-Wan finished the job where it all began in the deserts of Tatooine. Maul's first "death" on Naboo meant that his powerful ship was left abandoned somewhere on that idyllic planet.
The Scimitar was originally given to Darth Maul by his master, Darth Sidious. And after the apparent death of Maul, Sidious reclaimed the Scimitar for his own personal use. He would put it in action sporadically during the Clone Wars and would continue to do the same once the first Galactic Empire was established. The last time it was seen, it was used by a bounty hunter called Chanath Cha on a mission to retrieve a ship called the Imperialis which had been stolen from Palpatine.
At the end of that mission, a droid named O-66 flew the Scimitar away. The Emperor had charged the droid with caring for the Scimitar above all else many years earlier. What happened to the ship after this event is unknown. Prior to the Chanatha Cha mission, it was housed in an Inner Rim space station called Imperial Facility 729-D. O-66 presumably returned to 729-D with the Scimitar after the end of that final adventure.
The Chanatha Cha mission occurred before the fall of the Galactic Empire. It's entirely possible that the Scimitar is still sitting in the docking bay of 729-D with O-66 maintaining it and waiting for orders from Palpatine.