He thought that he had recognized the girl in the crowd. As much as Lelouch should be surprised to see her here, he isn't. Someone that actively seeking knowledge and scribbling furious notes coupled with the fact she had said something about finding comfort in it such habits just sort of jives more with this Job. In fact, the girl is still taking notes. Amusing, but...

Lelouch reaches over and takes the note book out of her hands. Before Connie can say anything he presses a finger to his lips. Wouldn't want to disturb the lecture by talking, right? is exactly what he seems to be saying with the gesture.