When the petrifications start, there is even more suspicion around Harry because, like, he’s this weird-ass knife fanatic who slaughters trolls and stuff. The Polyjuice subplot probably doesn’t happen because they can use Legilimency on Malfoy. Instead, suspicion falls on this quirky little Ravenclaw firstie named Luna who they discover is an Occlumens, but she is eventually cleared when Harry witnesses her being bullied by her housemates while an attack is going on elsewhere.