My songs on Apple Music disappeared after re-subscribing it on iPhone

How to cancel Apple Music - Apple Support

"After your subscription to Apple Music expires, you'll no longer be able to play songs from the Apple Music catalog. Any playlists added from the Apple Music catalog or created using music from the Apple Music catalog will also no longer be available. If you use Sync Library, it will turn off when your subscription expires. Any music and playlists you had on your device before you subscribed to Apple Music will still be available."

That might happen as soon as – or shortly after – the subscription lapses; even if you later re-subscribe.

Apple does not save your previously downloaded songs or playlists created from an Apple Music subscription. Very little information is saved about you unless required for the service or subscription. For the Apple Music subscription, you do not own the songs downloaded.