Why on earth would you assume that it is stolen?
Maybe he works in the same place as I do, and got it through C2W (ooh, how dare a non-cyclist think about owning a £600 MTB!) and then realised that he doesn’t need it.
Or maybe he just went out one day and bought himself a half decent bike because his mates ride up in Cwmcarn and he wanted to join them. And then he decided he didn’t like riding bikes after all.
I’ve got a friend who bought a brand new kayak last year and sold it after 2 trips out – would you report his sale because he’s not a great speller and can’t tell you exacly what brand his paddle was?
Jeez, find something better to do with your life! 🙄