Sorry to hear of your loss.
Your best bet would be to
contact Sonos directly to discuss it. It's unlikely that they would post anything here on this website, since there's less opportunity to prove whether you're the original owner or the "new" owner.
And to be honest, I'd wait until Monday and call them, it's unlikely that the Twitter or Facebook folks will be able to help, it seems much more like a voice contact would be a better solution.
Usually they require you to contact your local police, then have them contact Sonos.
