Noting the dearth of miracles reported at Lourdes, France, Lawrence M. Krauss appears to make several assumptions. In a nutshell, he is saying that the number of miracles reported at Lourdes and recognized by the Roman Catholic Church as legitimate is solid evidence — almost proof — that miracles do not occur.
One thing we do know is that if a single miracle occurred at Lourdes, Krauss would be proved wrong.
Another assumption Krauss appears to be making is that God is some kind of spiritual gum machine: You put something in and something comes out. If true, that would betray an incredible ignorance of the church or its thinking on the subject.
One wonders if Krauss would recognize a miracle if one sat down and bit him on the ankle.
Krauss notes that when scientists have a new idea, they "try to prove it wrong as well as right." Until fairly recently, the same was true of the Catholic Church when it tried to determine the veracity of miracles.