Sonos steals my music when I'm on the road

Is it possible that someone at home is using Spotify?

No, nobody is home.

As a test, make sure that something other than Spotify is selected on your home players as you leave the house.

Overall this will be difficult to diagnose because you are away from your system. If this happens regularly, I suggest that you submit a diagnostic as you leave home and log the confirmation number. If there is an event while you are out, submit again when you return home. Then contact SONOS phone support. Maybe something will show in the diagnostics.

Possible fringe case: If you allow guests to play Spotify on your system using their phone/pad, their Spotify client will remain attached to your system unless you select another source on your system. Users have reported departed guests remotely starting Spotify play on a system. I don’t recall any reports similar to yours, but I wouldn’t be shocked if your Spotify client and their Spotify client remain “entangled”.

Only I am using the Sonos speakers from the one iPhone, so I don’t think there is entanglement.

Aren’t these speakers too expensive to have to remember to change them to something other than Spotify every time I leave the house???

Does this also happen when you change to another source (not Spotify) before leaving home?

I don’t often use other sources, so I don’t know.  I’ll check.

If this is the case, it is a Spotify “feature”.

Another fringe possibility is an alarm triggering.

Why would Spotify randomly change speakers when it’s in the middle of playing?  I have used Spotify with other speakers and never known it to change.  Still, it is possible something about the interface with Sonos that triggers it.

I don’t see how that would be the case, but regardless, there aren’t alarms for the times it happens.

Having the same issue. Have done some troubleshooting but it still happens consistently.

Did you try changing the source in Sonos before leaving home?