How do I file a claim for property that has been abandoned for 6 months?

You will need to check with a real estate attorney who has experience with abandoned properties. It's best to choose someone who is familiar with local laws concerning these types of properties. Usually, an asset management company will take over abandoned properties if the mortgage goes into arrears, but it may take a long time for the home to be sold. Alternatively, the county may auction it off if it's gone into foreclosure and default. If there is no mortgage, then you will need to contact the owner. An attorney can help you with this.