I am sorry you have lost your money & I hope it works out in you're favour. I really can not understand the attitude of the police in these matters. Transactions are very easy to prove nowadays.All the evidence is there . This is surely fraud something the police are supposedly determined to tackle. I agree with the other contributers that that some more details would be good .Good luck.
It can happen and the cost and time is nasty.
I've had one problem from here, and it turned out the guy was just being useless/difficult. Fortunately had his name and address and telephone number. Eventually, told him there were forum members close by, Wales, and they would be knocking on his door. I'd also be ringing him every day before work too to find out if they had been because it could be any time. Finally, some cash arrived in the post.
Scammer or being useless... waiting for some cash and bought something he couldn't really afford.
There are legal ways to pursue this.