After an environmental clearance mission went wrong, Kybo was stranded in Reigate, England in 1884, bound in chains, and exhibited in a circus performance. He initially met the Sixth Doctor when his ship was crashing. When on Earth, he started to learn English and on the Doctor's encouragement started to write poetry. On the planet that he was clearing, he was affected by the Aetius who told them of their plight.
The Sixth Doctor's companions from stage plays are difficult to assert with certainty, as different actors played the Doctor in the same play. If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.