The Starfleet ship on which Cristóbal Rios served as first officer, struck from the records after Captain Alonzo Vandermeer killed two synthetic envoys on secret orders in 2390 and then took his own life.
The USS ibn Majid is the ship behind the past of Cristóbal Rios in the first season of Star Trek: Picard. She was a heavy cruiser commanded by Alonzo Vandermeer, whom Rios loved as a father. The ship is named after the 15th-century Arab navigator Ahmad ibn Majid.
As Rios tells it in Broken Pieces, in 2390 the ship made first contact with two envoys, Beautiful Flower and Jana. Vandermeer received a secret order from Starfleet Security, in fact from Commodore Oh, to kill them at once or see his ship destroyed with everyone aboard. He obeyed, confessed to Rios and shot himself.
Rios hid what had happened, and Starfleet classified the incident and removed the ship from its records. He left the service a broken man. Only when he sees Soji, the image of Jana, does he learn that the envoys were synths from Coppelius.