Really sorry to hear about your bike, I’ve had one of mine stolen in the past and it’s horrible! Thankfully you’re insured and you’re hopefully going to get a reasonable deal through your insurance.
But
I may have been a little scathing in the tone of some of my posts. But if you nicked my bike or bought it under the likely circumstances described to me by the police you are part of the problem not the solution. If the circumstances are different, perhaps the seller did invite you into their home and appeared completely plausible, then “sorry” you’ve very likely got my bike and that doesn’t make you an idiot, we can all be conned.
Buying a bike in a car park or somewhere out in the open wouldn’t seem all that dodgy to me. In fact if I was selling one of my bikes on a trustworthy internet site, never mind gumtree, the last place I’d be inviting some random punters would be to my house to have a look through a garage full of bikes!
I’d only ever sell bikes well away from my house in a randomly picked car park!
Still, they possibly would have realised what was going on when they met the guy, depending on what the the thief was like in person!
I hope it turns up eventually through word of mouth or such!