This is an act of cheating involving cyber techniques.
Therefore a complaint with the cyber crime police is maintainable.
If the concerned police is not responding properly then you may approach the higher police officer with a similar complaint seeking its intervention and direction to the concerned police to initiate proper legal action on such cheating activities.
Why did you not verify the veracity of their claim through your other sources ?
Such fraudsters are abundantly prevalent through such social networking sites, therefore it is the buyer who got to be beware of all such fraudulent activities instead of looking for remedy at a later stage when they have already stand cheated.
Approaching consumer forum on this may not fetch you any fruitful result.