Actually, if you signed a contract and provided a rate, and they accepted it and they didn't pay you, they have (I am not a lawyer so in my opinion and this isn

Actually, if you signed a contract and provided a rate, and they accepted it and they didn't pay you, they have (I am not a lawyer so in my opinion and this isn't legal advice) violated the contract. That may mean the NDA is not enforceable, depending on the terms. If you have not been paid then you also still have copyright over the code. For small claims, I think you want to be able to prove that you invoiced them, then serve them. Or talk to a lawyer.