"The Quest for Saint Aquin" is a science fiction short story by American writer Anthony Boucher (1911–1968), originally published in 1951 in New Tales of Space and Time.
The central character is a crypto-priest named Thomas who is charged by the crypto-pope with finding and reporting on the final resting place of a semi-legendary figure called Aquin.
Thomas is provided with an intelligent multi-terrain transport vehicle called a robass ("robotic ass"), to assist him in locating and visiting Aquin's tomb.
Helpless and naked in a ditch, he is ignored by all passers-by, including a fellow crypto-Catholic, but Abraham, an Orthodox crypto-Jew, rescues him and nurses him back to health.
Ultimately, Thomas does locate Aquin's tomb, only to find that he had been a robot, and that therefore the legend of his corporeal incorruptibility was true...but not in a miraculous sense.