I have solved the great mystery of why many of us have no record of this woman.
Bad news: She isn't a Sandridge at all. Lucy Seamands was a KEATON.
Refer to the following:
George Selden Wallace, Cabell County Annals and Families (Seamonds), Pg 484-485, Cabell Co Public Library, 455 Ninth Street, Huntington, WV 25701, 1001008985. "SEAMONDS ...Elijah Seamons married a Keeton, sister to Mrs Justine Keeton Sandridge, wife of Reubens Sandridge, who were early settlers in Cabell County, and it has been said that the two families came to the county at the same time, as they both lived near Barboursville, one on Mud River, and the other on Merritts Creek, a tributary of Mud River."
Her sister Justine Keaton married Reuben Sandridge (son of Stephen), and I bet people assumed both sister's last name was Sandridge, but it was Justine's married name. So Lucy's maiden name was Keeton, not Sandridge at all, that's why we can't find her.
INTERNATIONAL GENEALOGICAL INDEX
International Genealogical Index, v4.01, Film No. 538597:"Lucy Keaton, Sex F, Born Abt 1785 Orange VA, Father James Keaton, Mother Ankey Ballard"
International Genealogical Index, v4.01, Film No. 184740:"Lucy Keaton, Sex F, Born Abt 1788 Orange VA, Father James Keaton, Mother Ankey Ballard"
International Genealogical Index, v4.01, Film Number: 178006, Page Number 48, Reference Number 1496; and Film 177938, Page 1110, Reference 41583: "Lucy Keaton, Sex F, Born Abt 1788, Orange Orange VA, Father: James Keaton, Mother: Ankey Ballard."
This is better explained and documented at: