I'm not sure if this info will help but maybe. A while back I needed some medical records regarding my depression/anxiety and treatment. I requested the records from two mental health treatment facilities where I was treated... one public and one private. I couldn't get the records. Both facilities response was that they only store client/patient records for a certain length of time and then they are destroyed/tossed. I don't know that all treatment providers do things that way. I was never in any type of hospitalization program though.
I don't think your concerns are far-fetched or even unreasonable but I don't think it's very likely that your medical history will come back to haunt you in any way.