Dropped object in the windscreen!!!!

Well I am back after almost 5 weeks holidays, 2 of which we spent visiting Shark Bay, Coral Bay and Exmouth. All went well except for one thing on the way back 2 weeks ago. We were about 20 km from the Wooramel roadhouse (approx 100kms south of Carnarvon) catching up with a car and its trailer. It was a long stretch of road and I was about to overtake when a stick between 1.5 and 2m long lifted of the trailer and flew as high as 20m in the air. Since there was another vehicle behind me who had been following me for about 20min I couldn't just hit the brakes so I just slowed down and gently touch the brakes while putting my nose against the wheel to see where this bloody stick was. It was so high I had to put my face against the wheel to see it. I though for a second that it was so high we will simply go underneath without any problem, but as soon as I thought that it started to come straight down towards us like a spear. I tried to avoid it but unfortunately it hit the top left corner of the windscreen and made me fishtail a bit causing a bit of fright to the wife and my parents. I then had to chase the guy to stop him and he tried to argue it was not off his trailer. Lucky the car behind us had stopped as well and saw it too cause without a witness I would have had difficulties claiming that to my insurance. After a few attempts to argue it was not off his trailer he finally backed down and say it was probably but later on said that in fact someone else packed the trailer for him so he couldn't know what was in it!
We were very lucky that stick bounced back after pushing in the windsreen and leaving a hole a cracks in it. If it had penetrated fully my mother would have been empaled to her seat.
We then did the 20ks to the roadhouse where the owner kindly gave us some cardbord and tape so we could cover the hole and smashed area and tape the cracks. We did a good job since we managed to do the 900ks left back to Perth like this. Lucky it hit us in tha corner cause it was not obstructing too much my vision. Any other place would have made it hard to drive anywhere.
I have had the windscreen replaced and am now waiting for the insurance to sort out the claim, but I had to pay $250 excess. They told me I would lose it as well as my no claim bonus (resulting in a 20% increase of my premium) if they can't make this guy liable for the damage. I guess it should be easy since we have witnesses, but am worried this guy might not be insured. Does anyone know if the insurance will be successful if that's the case and if not what else could I do to make the w#*nker pay? I already went to fill a accident report to the cops.
Sly.