Giving him more time is honerable of you......a phone call, an email a status update of your parts would be honerable from him....
You know, you can still get the sherif involved to access the situation and get your parts or verify they are there WITHOUT taking any legal action to create problem for matt if they are not justified. If you go there with the sherif and he does not have parts, wont return money paid for services not provided then at that point you know what you are dealing with and if necessary can take appropriate legal action at that point.
You need an accounting of your parts , PERIOD! If matt wont provide that with communication then pay him a visit with sherif to record and verify what is going on. Matt may simply may hand over your parts and money. Human nature at this point is to assume the worst. He may have all your parts sitting on a shelf, he may not....its time to stop HOPING---and start finding out. Getting a sheriff involved does not get him in trouble with the law, It may save him from lots of legal trouble and more drama in his life. Just my .02 Jou each have to do what your heard and head tell you is best for you.
I express all this, only because I have been through the EXACT same thing and it didnt end well. Had I taken action sooner, it would have been better.