I'm sure he heard the song, once, in 1998. Maybe a handful of times since then. I've read (I think in Mark Horowitz's book of interviews with Sondheim) that Steve doesn't generally listen to Broadway music at home and rarely listens to albums more than once, when he first gets them. So I think it's totally reasonable that he didn't remember the song.
Hell, I've listened to Parade dozens of times (and seen the show more recently than 1998) and the name doesn't ring a bell with me.
