just a thought as i never read your other thread.
are you sure they were policeman ?
it could be a scam where the seller sells a bike, then gets his mates round to your house ( as he has the address, make of bike etc), says there police, you’ve bought a stolen bike etc etc, they take it, and the now seller has your money and now the bike.
or am i just paranoid……… 😯 😉