Hello sorry to greet you in these circumstances, I do know that one of the unfortunate things about dealing with schizophrenia is that the disorder makes the person very unpredictable. Hitchhiking is not a leap for someone with schizophrenia, I also know that mental hospitals are notorious for being abusive to their patients. I say that to say don't real out foul play, but I also encourage your family to consider the hitchhiking theory. I am actively working on a podcast that shines light on missing people and your aunt's case is one that has me puzzled. I have ran my head into a wall with my theories, once I have edited the podcast I will upload a link here so that you all may take a listen.