Hair today

I'm looking at two people in the lecture hall from behind, and thinking how similar their hair is. I wonder, if they wake up in the morning with each others hair, will they notice? I think they will but I don't know how quickly or how they'll make sense of it. Would they tell people that they've woken up with someone else's hair? Would they think they must have made a mistake and not have noticed the quality of their hair before? Would they go to the doctor [or hairdresser] or be scared of being thought of as mad?