Go to the steam room in the evening, I had this problem too and out of frustration decided to go to everyplace at every time and found the way to progress
Try reading dialogues sometimes, when you entered Instructor's cabin the MC said "hmm, where could she be? Steam room? Showers?" But you didn't read it.
I've been waiting for hange to come back but no matter how much i sleep she isn't coming back. Any help???