Pope springs eternal

The current incumbent of the papacy is making two of his predecessors 'venerable', according to BBC News. This means Pius XII and John Paul II will be just two steps away from sainthood.

The next step in the process is proving that they performed a miracle, defined by the OED as 'a marvellous event not ascribable to human power or the operation of any natural force'. The BBC phrases it as 'usually a medical cure with no scientific explanation' and this got me thinking. What happens if the Pope awards a sainthood to someone on the basis of a miracle, only for science to find an explanation later on? Is the sainthood retracted? Has this ever happened to anyone?

Calendar for 2014

June 23rd - Dave's Day
(Formerly St Dave's Day, prior to the discovery that his miraculous removal of a parishioner's ingrown toenail was accomplished using a pair of pliers rather than the love of God.)

Apparently you don't need a miracle to become a saint if you are martyred, which is why December 19th is the Saint's Day of Augustine Moi van Nguyen. Shouldn't Benedict XVI consider getting himself killed trying to convert heathens to Catholicism? At least then he could guarantee himself sanctified without having to worry about battling the logic of medical science.