I went to high school in the early 90s, at the dawn of graphing calculators but before teachers were wise to the "notes" trick.

One time before a calc test I dropped my graphing calculator. The battery door popped off and the batteries popped out. The unit was otherwise unharmed... but my cheat sheet in the notes app was gone!

I nearly crapped my pants.

Luckily though... as most cheaters know... to make a decent cheat sheet you actually have to comprehend the material first. Half the time you wind up not even using your cheat sheet. Luckily for me that was the case. I still did well on the test.

I am a little older than you, so my cheat sheets were on paper. There was definitely something about miniaturizing notes that reinforced learning. I made dozens of cheat sheets but never had to use one.

Yeah, the vast majority of mine were on paper!

    There was definitely something about miniaturizing notes that reinforced learning

We have to comprehend a thing in order to summarize it, right? The more compact the summary, the more comprehension required. =)

I also did this, but never got around to storing test-related materials in my phone. It was mainly for preserving my goofing-off programs.

Not phone. Calculator.