Greg insists that he really was attacked by a giant, ambulatory number 13. Having only heard the story secondhand, I’m assuming that there was someone dressed up in some sort of mascot costume, perhaps as part of an educational play for children. That, combined with the fact that he was also assaulted by thirteen sports fans wearing number 13 jerseys for sitting in seat 13, leads me to believe that he got the worst of the bad luck out of his system.
Of course, he may have angered more witches since then that I’m unaware of. He’s always doing that sort of thing.