Apple Music library

Only Apple know the answer to that. I believe they have stated somewhere that downloaded songs and playlist remain in existence for 30 days after expiry of the subscription (though not playable, of course) but this is evidently not the case, aas evidenced by a number of reports in these forums. Whether this is a deliberate decision or some sort of an error, there's no way of knowing.

I'm afraid so. The general experience has been that downloaded songs and playlists don't survive the subscription expiring and then being restarted.

In the past when my subscription had expired and I had resubscribed everything was still active. Why has that changed?