Yes, it should be investigated but in practice the police will probably decline to act unless you have bombproof evidence, not only that you have been scammed but that others have too. Hearsay via forums, is not enough and they have other priorities so a lot of crime, and especially fraud, goes uninvestigated. Some while back, a bunch of Somalis managed to persuade the idiots at RBS to send a replacement credit card for me to their North London address despite the bank knowing full well that it wasn't my billing address. Fortunately it was intercepted by a good neighbour who became suspicious and alerted me. The bank simply cancelled the card and issued me with a new one - no apologies, the police said that no crime had actually been committed - money stolen(!) so they couldn't act. Basically it is so common that neither could be bothered. The banks stand any losses and simply up their charges to their customers to cover them so we all pay in the end. The police are probably more interested in chasing Cliff Richard.
In this instance the bank has done nothing wrong so won't be interested.
No, it isn't fair but that is the way it is. A private prosecution through the small claims court might produce a result but the chances of it being enforced will be low unless the scammer cooperates, which of course they won't, and the buyer will probably then be even further out of pocket.
Colin