When someone says 'hello, how are you?' and you think they are talking to you when they are actually on the phone. This happens all the time at work, wish people would not use their phones at the till.
In choir when I thought the conductor pointed at me to sing a solo so I stood up and then he said no Rachael, I was actually pointing at the girl behind you.
Turning up to my music mock GCSE an hour late. My SEN teacher had made this big colourful timetable and put the wrong time on.