Most scam attempts on here are so poor that it's blatantly obvious that they're a scam.
There are usually a lot of tale-take signs to look out for too as mentioned above.
Make sure to have your trust network set to default or on a low level and always look through a user's trusted and I trusted feedback.
It's also usually best to use escrow as that way both parties are safe. If a seller refuses to use escrow then it's more than likely that they won't be able to deliver said goods and you know to steer clear.
I advise you to open a thread in the Scam Accusations board and posting proof to backup your claim. It will help potential future buyers as well as help clear up any questions people have regarding this dispute.