Lost Music from 6S

[Didmanoohf]

I was just listening to Spotify on my 6s when there was a glitch that **bleep** my whole phone down.

Upon switching the phone back on, all my offline albums and tracks had been deleted. I switched the phone off again and the albums reappeared but no tracks, only the handful I had saved into playlists.

The albums still show as available offline but once I drill down, nothing appears. See screen shots.

Anybody else experienced this and what is the resolution, if any?

Thanks in advance.