Left my phone in my pocket during my GCSE exams a few years back. Alarm repeatedly went off, despite me panicking to turn it off without being noticed. Exam invigilators went nuts trying to locate the source of the sound, but eventually pinpointed it to my direction. Was told angrily to hand the phone over, so I did. Luckily, the exam invigilator knew how much of a nerd and goody-goody I was, so let me off lightly with an "I expect better from you, don't let this happen again". Scary experience nonetheless.