How to recover missing files from my iPad?

I’m facing the same issue that a lot of iPad users are facing. I had a document on my iPad (stored locally on the device, not in iCloud), I annotated it with the Apple Pencil and after a few days, I couldn’t find it in the folder I had put it in, so I searched for it, it came up but wouldn’t open and then after trying to click it a few times it was gone, it literally vanished.

THIS IS UNACCEPTABLE.

PLEASE FIX THIS APPLE!!!!

[Re-Titled by Moderator]