Buyer Scam?

[Valvoltec]

Looking through the classified section with me,my son spotted a car for sale.
I was asked to buy it with a combination of his birthday and Christmas monies.
I duly replied and asked the seller politely to sell me the car.
Payment was specified via Paypal.
I received a reply back stating that he would not be selling the car to a new member with 1 post,and that I was more than likely a scammer.
I have purchased before on here and gave the username of that member,I also gave
My eBay username.
I explained my son had his heart set on the car and asked that we could perhaps use an intermediate.and suggested a well known eBay seller that is my lms.
I received a reply agreeing this,yet today the car is sold?
So what scam can a new member pull off if I sell via Paypal,I have the money and the goods, I send via insured and signed for delivery,I am covered for damage and proof of delivery.
Paypal gives a delivery address,
I am really a bit baffled by it all,my son is very disappointed,, I feel tarred by a brush that is not me.I have bought and sold dozens of things online,including cars and a yacht,met some lovely people,had a few problems,quickly sorted..
Perhaps somebody can enlighten me.