Surely everyone on this list hopes you persevere, and keep sharing the details on your search process.
Meanwhile, for further encouragement, I recommend the 2009 book, "Annie's Ghosts: A Journey into a Family Secret" by Steve Luxenberg. He is a Pulitzer prize winning reporter, who learned only after his mother's death that she had a disabled sister, Annie. His research started with a Michigan asylum & hospital, but led to some unexpected experiences for him. All this drew Steve's extended family closer together. His interviewing skills and caring approach can be applied to research on patients & records in other states. I'm only halfway through it, but I think he found more cousins. A good winter read!