Same happened to me some time ago. Admittedly posted for sale by a good man who bought it in good faith. I bought it back for what he paid.
If I were you and it’s worth it, just buy it back, but offer as little as possible.Chances of police help is negligent
My mates stolen bike has just turned up for sale on fb market place. What’s the best plan of action from anyone that has had a successful outcome ?!