Dispute with Auto Insurance Appraiser

Hey everyone, I have some pretty serious questions/insurance issues that I need some help with. First a little background: About a month ago I was hit on my front left by someone who failed to yield the right of way. Her insurance company claimed liability and after 3 weeks my 2000 Ford Ranger was andquot;fixedandquot;. After bringing the truck home I noticed there was a small coolant leak. I had asked the Ford body shop to inspect the whole truck top to bottom as the impact was pretty hard. After hitting me she pushed me across a lane of traffic and we ended up in a grass area on the side of the road, and a sign was lodged under my truck Apparently Ford did not do this, thus me discovering the leak and not them. I took my truck to an very reputable mechanic in town, and right away they recognized that an impact had caused the damage. In their wordsandquot; natural wear and tear does not happen in this area, anyone who knwos engines should know this. An impact is needed to cause something like this. After contacting the insurance company, they sent the same appraiser who appraised the damage the first time. A little background about this guy. When he originally appraised the damage I asked him to look at the engine as the check engine light was on. His response was that as an appraiser he does not check the insides of vehicles, only estimates the outside damage and that he was not a mechanic. After checking my truck today, he said that in his opinion, after inspecting the engine, the damage was not caused by the accident. Everything he claims is in direct contradiction to a certified and very reputable mechanic. I asked him what exactly he was basing his opinion on, he mumbled something about a gasket and kept repeating, andquot;its my opinion and thats what I'm reporting to the insurance companyandquot;. He also claimed that a hard, front side impact in which a car that pushed a 3200 pound truck over a lane and into a grass area would have zero effect on an engine, which sounds completely ridiculous to me. So basically he had nothing to substantiate his andquot;opinionandquot;. Naturally I have contacted the insurance agency and disputed this, but now it is the weekend and I won't hear anything for a few days. So, I'm really just kind of curious how an appraiser who self admittedly is not a mechanic ,and refused to inspect an engine, comes to the conclusion that the damage is not accident related, directly contradicting a reputable mechanic. Is this their job or isn't it? I also find it interesting that with this added damage, the truck would have most certainly been a total loss as it is over $1000 in additional damage. Do I have any recourse here? I now own a truck that should have been totalled. Any help or advice would be appreciated. thanks Jon