iPhone suddenly lost ALL my music... WHY?

I was just sitting about to play music via aux chord in a car and then out of all my 1,000+ songs I'm only left with 4...

The problem is, I don't even have all that music on my computer anymore and I've already tried to restore my most recent backup and it did not help. I also tried Googling this and all I get is that it's a bug.

I don't really care about the solution for this, I just want to know WHY??? because what's the point of fixing it when it could potentially happen again. This is horrible and almost makes me want to convert to the other side... SMH