When I was a student, every middle school student with a TI-83+ was keeping notes in the BASIC editor, and the future programmers were all automating their work in BASIC. Teachers started wiping calculators before exams, and kids started backing up their files to the calculator's ROM to work around it.
Remember, this was the age of T9 typing, we weren't gonna let the lack of a keyboard stop us...
I always found notes and books for open book tests to just make things harder. Sure, a single well made cheat sheat could be invaluable, but in general if you didn't know the material nothing was going to help you if you had to show work, which you do on all non-bubble-sheet exams.
I've only ever had a handful of open book tests in my life, but I just mean that even when you're _allowed_ aids, they're not actually useful unless you have some base understanding anyway.
Remember, this was the age of T9 typing, we weren't gonna let the lack of a keyboard stop us...