heh, in order to be prosecuted, there need to be organization that oversee and regulate the sales of musical instrument, prolly with penal code to follow.
Unfortunately, there is none of such nature if iam not wrong. Closest is prolly ipos(intellectual property of singapore). But within their umbrella, whether or not it cover the sales of such instrument as an individual and not a pte ltd, is another thing.
Afterall, if the sales of such nature, where communication is done properly between seller and buyer, with buyer knowing that its a fake that they are buying, what can we say. It takes 2 hands to clap yeah.
The only thing that we can do, is prolly notifying the moderator of the forum and have them removing the ad. Anything more, we are prolly on a witch hunt on a fruitless trail.
Anyway, call police also no use, it aint porn or contraband item. They would prolly ask you back, under which regulation or law can they or organization regulation to take further action. Hehe, In my course of work, at time when needing them, thats the reply i get, "so what do you want us to do with mr/ms so and so and if wanna raise charge, under what law". To give them some credit, its not that they aint doing anything, but certain context, they aint too familiar with.
Hehehe, live and let live, just like piracy, we cant stop the movement, but at least on personal level, things can be changed. But if the person in concern is not willing too, whatever we can do, it wont be fully effective.