I'm aware, but Hibiki and Shizuka don't know that. They also don't know about Alexi's death either, so as the commanders they'll feel a bit guilty that they've allowed themselves to be so disorganized. If everyone worked together and buddied up they no one would have died. Though I did hope maybe Cherry could bring back Nu-Mu, but after rereading your post I don't think there's anything left of Nu-Mu to bring back.