Sonos playlists are stored on the speakers, not on your phone. As long as you didn’t reset your Sonos speakers, the playlists should still be there. Try unplugging your speakers from power for a couple of minutes and reboot your router and phone.

@Fidalgo,
There are many different sources for playlists within the Sonos App - some can be stored/held in the App (actually they are held on the speakers), or they maybe held elsewhere and merely ‘viewable’ via the App.

As an example, I have playlists that are created and saved in the Amazon Music & Deezer Music Apps  that are ‘viewable’ via the Sonos controller App, but if I disconnect the Deezer service from the App, then I will no longer see the playlists from that service.

So if your playlists were on your mobile and being ‘viewed’ via the Sonos App  and you have deleted them, then it’s likely they are lost, but it depends on where they were created and stored originally.

**Note: Music from “This Mobile Device” cannot be added to Sonos playlists as mentioned here:

https://support.sonos.com/s/article/3198

So I’m guessing your playlists are probably not held on your speakers, but were perhaps held on your Mobile and ‘viewed’ via the Sonos App, but that’s just my guess.

Thanks for your suggestions. Shortly after posting here, my playlists were back in the Sonos app. No idea why. But searching this forum I can see that many people experienced similar issues after updating the app.

All good now

You need to give the system time to sync with the app…..

Should not be necessary. Takes less than a second to get the list of playlists (of both kinds) from any speaker to the app.

The 'disappearing playlist' is indeed a common one. Happens with Sonos generated playlists as well. Yes, they are fixes, such as unplugging/replugging a Sonos component, but why hasn't Sonos fixed this. One solution that works for me is SonosSaver. Let's you export your Sonos playlist to your music collection or wherever. Then should Sonos lose your playlist again, just import what you've exported.

Get it here: 

https://mrupp.ch/