Okay, as others have said below, you can have a lawyer investigate this and give you advice. And only lawyers can give legal advice. But your question does not imply litigation or other legal action. It simply implies that you want information about the availability of insurance that might cover an injury. So let us not over-think this. Why not just ask the property owner who hopefully bought insurance to cover exactly this kind of situation? If you don't know who owns the property, you should be able to find out at the county courthouse (or online). And if you feel uncomfortable asking the owner in person, then write a letter or send an e-mail.
P.S. The mortgage holder (i.e., the lender or someone who bought the mortgage paper) probably will not provide insurance information to someone who calls. Privacy issues and all that.