Lots of stories like this. My favorite is Judee Sill - disappeared, died of an OD pretty much penniless. Music ahead of its time with layered recordings, rediscovered decades later...
Collie Ryan is mine. She did three albums in the 1970s and then basically disappeared. I became aware of her through the use of her (amazing) song "It's Gonna Rain" which was featured on the soundtrack of Computer Chess (2013), a very weird (but good) film that seems to be about a computer chess tournament in the 1980s but gets weirder.
https://www.spinmagazine.com/2013/07/collie-ryan-its-gonna-r...
My favorite is, fortunately, a lot less depressing. Sinead Lohan, right on the cusp of making it big, touring with some of the biggest names in folk at the time. Realized she didn't like the music industry so she stopped and retired right then and there. I have no doubt she'd be a legendary folk name if she continued. Whatever It Takes is my favorite song by her.