[weregiraffe]

>you could not leave exam for the toilet without asking first and then being followed out by a watcher, which then would follow you back and check the toilet afterwards for notes.

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.

[silvestrov]

Notes in the toilet were mostly for passing to other students.

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.