Lyndal's right and your post doesn't give enough detail. It's as clear as mud.

When you buy on ebay, that sale is registered by ebay, the seller doesn't have to do anything & can't hide it.

Did you buy on ebay at all? It doesn't sound like it.

Or did you buy on ebay but then follow his instructions and pay into different paypal or bank account for the item prior to pick up?

Did you post the item back to him or return it in person?

If you had paid cash on pick up, I can't figure out why you didn't insist on a refund when you took it back, that's the sticking point here.

Instead of ringing, why don't you go around to the warehouse again and ask for your refund in person? 

When you want to buy something on ebay, always buy through ebay, pay for it via paypal and never listen to any excuses why you should do it differently. If it is a pick up item, pay cash but check the item out before you hand over any money and if it isn't what you want, walk away without paying.

.