Scam

Hello EDWARD. When you purchase items on Trade Me (Especially larger value) you need to pay with Ping. That way you are covered by Trade Me's buyer protection. It's a lesson many learn the hard way. 

Trade Me are correct, there is not much they can do if you have transferred money yourself into someone else's account. However they will be able to assist with the Police investigation and send through the details on file they have. 

The drop of good news is that it's next to impossible for a person to open a bank account in New Zealand with false details. That account will lead to a real person. Relatively easy for the Police to get that info and follow it up. I find you do need to be a squeaky wheel to get the Police to act though. I have been in a similar situation many years ago. My scammer was eventually arrested at the border coming back home from the holiday he took on my coin. His parents bailed him out, and I got my money back. 

Good luck, and update this post with how you get on. 

When you made your deposit online I assume you used the Account check system? That will at least give you the sellers name. From there you can do so more searching for more details on the seller yourself.