Here is a story on the same line as yours, when I had my 71'cuda and was working along side of a guy that I thought would be a good person to help me restore the car. To make a long story short, when I was not there one day he decided to take the front chrome off the windshield and he managed to put a nice crack across the windshield.
When I saw my windshield later that evening, to make worse on the story, he stated "the windshield must have been cracked when you (meaning me) before I brought in the car."
Man was I pissed, so I pulled out some pics of the car the day I brought it in to him and pointed out the very non-cracked windshield. Not to mention the fact I would think I would notice a 20inch crack on the windshield. He still denied it and that he wasn't going to pay for a new one because these things happen.
I ended up looking for replacement glass and here is a kicker, I bumped into a guy that had a better piece of glass than what was in my car. Come to find out that he was 2nd owner of my car, I was the 4th and gave me a deal on the glass ($50)!
The moral of the story is even though it might stink that you had something similar happen to you. You never know what adventure and possible situation this could present to you. BUT on the flip side you never know what good people you might meet along the way, may even present a better part, a good story or even better show you pictures of your car when it was almost new!
Chin up, what is done is done and can't be un-done. Just look forward to some very new, pit, crack free glass.
Something else to keep in mind, if he is a larger shop, they will have insurance and with pictures before and after I can't imagine that any small claims court would side for them. However it will probably cost you more in time and money highering someone to take your case for a $200-300 repair for new glass and installation.
Good luck
-Jim