It wasn't a surprise that he knew about that day. If he didn't know what happened would've been a much bigger surprise. Secrets were rarely kept secret in the Inner Circle. Information was currency, power. Rabastan was the sort to seek it out wherever possible. While she didn't believe that he was seeking the position of Dark Lord for himself, she did wonder just who it was that he was working with. Theodore Nott was the obvious answer. Of course, like she was well aware of, Rabastan played multiple games at the same time. No one, besides himself probably, knew them all.