itunes deleted music
I was running iTunes 12.1.1.4 (I think, it's been updated as of now so I can't double check). I plugged in my iPod Touch, which is not set to automatically sync. I got a new CD that I ripped to my computer running Windows 7. I dragged the new files to the iPod and I saw "Waiting to update" as my status. After a few minutes I find that ALL my music has been removed from my iPod except the tracks I purchased through iTunes.
How pleasant.
I own all my music, so I have copies of it not only on my hard drive but also in physical format on CD. But come on. There's no possible setting that should wipe out all the tracks not purchased through iTunes.
That said...what, in the eyes of Apple, did I do wrong? How could I have averted this disaster?
iPod touch, iOS 8.4