This case has been well publicized. A person who remained unidentified in a hospital would end up being publicized as well. I'm sure all hospitals in the region would have a way of figuring out Barbara's identity pretty quickly, especially as the admission would have occurred on the day she went missing, and hospitals would report an unidentified person to their LE resource officer right away.
I'm sure there's a lot that's been done that we don't know about, as well. My fear is that with SBCounty's enormous size and the sheer number of calls the Sheriff gets daily, the attention to Barbara's case will fade. The missing posters would keep her case more visible. There are posters still up at Grand Canyon for people missing years ago...occasionally someone is found.