It's interesting to see others thoughts on this. Because I have worked in psychiatry as a nurse and NP, I immediately jumped to conclusions as to what happened.
When I saw the "State Hospital" part I gathered that she was chronically mentally ill and had been likely committed for weeks, months, or years. The only place that I've ever seen or taken photographs of a patient are for psych hospital charts. Back in the late 70s and early 80s patients would stay at the psych hospital for an indefinite amount of time and that "revolving door" hadn't really started swinging. Insurers and the government were still paying for care.
Which leads to the really weird part. We've seen cases where people are in legal limbo because they do not have a name/ID (notably Benjaman...ooh, I'm forgetting - need moar coffee). How would this woman have been committed, legally, without identification? Perhaps the legalities/billing were a bit more lax at the time?
So with the data provided my brain jumped to this: Jane Doe committed to SC State Hosp for severe mental illness. On 2/15/82 she disappears and is unable to be located. Later on her skeletal remains were found on the grounds and it is determined that she perished as a result of an accidental fall. The state of the remains matches up closely enough with the date last seen so they call 2/15/82 as the date of death. Nobody wanted to admit that this woman might have been out there for days before she succumbed to her injuries. Or, the injuries were so severe (e.g. skull fracture) that immediate death from her injuries was probable. Just speculation.
So yeah - more information would be very helpful!!