I am sorry you are having to go through this and due to some body's negligence you have had your integrity challenged, been anxious and lost sleep. It is hard for me in these times to share news that is maybe not what you expected. I have reviewed your facts back to the beginning and the only thing I really see that stands out as a cause of action in Texas is negligence by GM. So you know there is a book on my shelf called "Texas Causes of Action" and unless you have a recognized cause of action then you can't bring a successful lawsuit. Here it is quite evident that GM Finance was negligent in their handling of the VIN, but this is really more related to the negligently providing it state farm than to them simply mishandling the information. By that I mean if they had left documents in the trash that had that information on it I am unaware of any Texas cause of action you could bring. This is where it is "not right" and "not fair", but perhaps legal. If they mishandled your social security number there is a federal act that covers that, but typically any lawsuit is brought by the government to force compliance by the company.
To have negligence you have to show that the party owed you a duty and that as a result of their failure you were damaged. I can see you proving a case of negligence here, but you damages may be somewhat limited. You would be entitled to a loan that was handled correctly so any over payment would be damages. The fact that you were investigated by State Farm would be devastating to anyone trying to advance in the company, but unless there are other facts that show that GM played some role in it, it comes down to state farm conducting an internal investigation. If GM had made some statement to state farm that you were involved then you could sue GM for defaming your character.
I think it might be worth meeting with a local consumer law attorney to see if the claim is worthwhile. Note I don't discount the fact there is a claim, but would want you to weigh that against the cost of litigation and more importantly the time involved (9-18 months typically). I would recommend you go here http://www.consumeradvocates.org/ to the National Association of Consumer Advocates and search for a consumer law attorney near you. You can likely meet with one for free and it would be a good way to have a fresh set of eyes look over the problem. It would be helpful if you presented it to him/her in the same fashion as above with the bullet point and brief history.
In the alternative I would see if I could demand that GM put you back in your original position and then contact a different bank or credit union and see if you can get them to refinance it so you are no longer dealing with GM. I am sorry I can't give you the exact answer you may have been looking for and as damaging as something like the state farm investigation is I recognize that you want to hold someone accountable for what you went through.
If you have not already you should take a copy of the letter from G.M. to your employer's HR department and ask them to include that within any investigation file they maintain on and that after both they cleared you and GM admitted fault you would believe that you advancement options are limited in any fashion based on this negligence you didn't ask for by GM Finance.
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