That's not how you do it. The notes are in your pocket. You go to the toilet, read the notes, put the notes back into your pocket and go back to do the exam.
In many exams we were allowed to bring our own notes. Those are unusable if you haven't learnt the material, as you then don't know what to look for.
But a small note with a math solution could help another student a lot.
exact same processes with external monitor etc. but with the backup exam papers that was different to the ones everyone else already did.
which is kind of in contrast to university (organised by the institution) where someone stole the exam paper for a difficult module in our final year. so they assigned one of the past year’s papers instead, as if everyone hadn’t memorised it already.
one of the benefits of scale with central organising bodies where you have to get things right (organising GCSEs nationally) is being forced to prepare for edge cases because they become a lot more common.