Well, the three hunters in Free to Be knew Sam was a demon-blood addict, and they've probably all been primed by Gordon's "SAM WINCHESTER IS THE ANTICHRIST" campaign, as well as the rumor that they opened the devil's gate in AHBL rather than closed it, so I think it's possible that word that Sam set Lucifer free has spread. And there's always the possibility that Zachariah's been stirring the pot in that direction, as well.