Disappearing iTunes

I am a very organized person, I keep a written log of all of my purchases. For the last ten years now iTunes that I have definitely paid for, entire albums, have randomly disappeared. It would take a great deal of explaining before I will believe anything except that Apple thinks we are all too stupid to know what we have purchased, or perhaps they think we are all too lazy to do anything about it. Has anyone else out there had this problem or is this just specific to me? For the record, iTunes should just continue to shit all over their paying customers, but I will never again pay as much as a penny for iTunes.