Cooper says and testified that he brought it up to Libby.
And IMO, even if all of the reporters knew of Plame independently from discussions with Libby, the indcitment still stands. That's my recollection, having read the indictment with exactly that fact pattern (reporters knew before Libby did) in mind.
The Indictment and Fitzgeralds statements alleged that Libby could NOT have learned of Plame from reporters because no reporters knew of Plame before Libby leaked the name. The idea that Plame was not widely known is becoming a joke.