Apple Music
I opened my Apple Music which I pay for and it wiped out all of my songs that I have downloaded???
iPhone 11, iOS 14
If you subscribe to Apple Music, you might be able to fix your issue by turning Sync Library off for all of your devices, then turning it back on again. Learn how.
If it is music you bought from the iTunes Store, you should be able to redownload it.
Redownload music - Apple Support