Were you ever able to locate your "missing" grandfather? Herbert William Sullivan?

I have a "missing" great-grandmother: Anne Fulcher.

My Great-Grandfather Alex Middleton Parish was married to Anne and had my Grandmother Maudie L. (Parish) Bruce and her siblings, then Anne suddenly dropped off the face of the planet around 1898 - he remarries Caroline L. "Callie" (middle initial A.on tombstone) Johnson and has a new flock.
Was told Anne was Native American.
Been searching for DECADES and still nothing - no birth date, no death, no records of any kind. Drives me nuts!