WA Shopping Centre Car Accident - GIO Insurance Making Me Pay for Damages?

First I had an car accident in New Park Shopping Centre almost 9 months ago, I was slowly reversing my Mate's 4x4 Nissan 4wd. I checked both mirrors on the sides and the reversing mirror and looked out the back, and slowly started to reverse out there was nothing behind me, at least from what I could see.

Then I heard a crash sound. I stopped and exited the vehicle to find a small Silver car had reversed at the same time but was directly in my blind spot. In other words, there was no way I could see him. We spoke and he tried to blame it on me. I gave him my business card and heard nothing.

Now Nine months later I received a letter from his Queensland Insurance Company stating that I now have two weeks from the letter arriving to pay them to pay $2547.04 or they will send debt collectors to me as well.

My Friend's car has no car insurance and I feel I wasn't at fault as the person had placed themselves in my blind spot. The damage to the car was from the centre to the right caused by the tyeare from the 4x4 coming into contact with there vehicle. I suspect they reversed out and didn't look and hit me.

As this is not a public road, how does Traffic law function in this process? I did the right thing and now Nine months later GIO Insurance are trying to get me to pay for the damages and his no Claim as well.

Please help to tell me and guide me as my best direction legally.

Thanks.