There are laws under your StateIt's an unfortunate reality that provide protectionState laws do not have strict requirements and licensing for business liabilities such as yourscomputer developers/engineers. Generally speaking If they did, ayour business structure would lien the property from the last date where the work was done. Often times, a Notice to Lien will sufficehave legal rights offered under State statutes.
$1000 or $100 is not the issue, but it's the principle. You provided services,Consider this a loss and as such, unforeseen events kept you from fulfilling them on a timely manner. I think the client is just looking for an excuse not to pay.
But, lessonslesson to remember for future projects. Make it clear in your Terms that such unforeseen events will only extend your project salarywages, not decrease it!them.