What do I do if my uncle is losing his memory and no one has power of attorney and the law will not give me?

He had one brother that is his full-blooded brother who lives in another state, also the half brother he had was his power of attorney but got caught stealing money from him so his power was revoked. My uncle went missing and I was asked to come get his impounded car about 6 hours south of his home. Then he was put in a hospital to where the hospital says he was admitted as a private patient and no one will give me any information on him what so ever, will not even tell his full-blooded brother. What kind of legal action do I need to take and do I have a legal right to his information, if not who would. His wife is deceased, my mother whom was his sister is deceased, and I have no idea what to do.