The Franciscan theologian Blessed John Duns Scotus died in Cologne in 1308. According to some Dominicans (wink, wink) when the vault in which his corpse resided was opened, he was found lying outside the coffin. This had led to belief that Scotus was buried alive since there is no other explanation for how his body got out of his coffin.
This story, however, is late and probably originated with naughty Dominicans trying to undermine Scotus' influence.
Apparently, the famous Thomas a Kempis, author of Imitation of Christ, may have been truly buried alive.
On a related note, fear of being buried alive led to the invention of the safety coffin.
Duns Scotus was beatified by Pope John Paul II in 1993. Scotus is best known today for his argument in favor of the immaculate conception of the Blessed Virgin Mary, which Pope Pius IX dogmatized in 1854 with the apostolic constitution Ineffabilis Deus. The argument of Scotus (and hence Pius IX) goes like this: Mary as a daughter of Adam required redemption like all other human beings, but through the foreseen merits of Christ's death, given in advance, she was conceived without the stain of original sin.