How to request an investigation on behave of auto insurance claim?

[Kate]

I rear ended the guy, and the only damages that he had is a small scratch. However, later I found out that he claimed that his automatic system also went down and he couldn't drive his car ( which is totally lie, after the accident he sat in the car and went home, even the policeman who was with us saw it), so for the replacement of that system he asks a lot of money, even thou he fixed it only after 1 month, that's what I saw when I got a copy of estimate from his insurance company, also it was saying that its a second estimate. The company never send me the first one, even thou I requested couple of times, and when I first called in the damages were much lower, than they are now. The thing is that my insurance was lapsed, so I have to pay our of pocket. However, at same time I see that the guy just tries to screw me. My question is how I can request an investigation or prove that its total bs to insurance company and let them know that its not going to happen. I even called couple of body shops, and they told me that there is no ways his electronic system on the front could be damaged from such hit, otherwise he wouldn't even drive back home on the day of accident.