How do I recover my Itunes Playlists?

All of a sudden, when i opened the Music app today, all my playlists were gone. The music files are are still on my computer, but no songs show up in Music, and no playlists. It's easy enough to move all the files to Music, but I had everything organized by playlist, plus I had 15 years of playlists that I really didnt want to just have vanish with no warming, and no explanation of how to save them before they were just wiped away.