Because Doc Wise's wife is listed as Mary A. [maiden name unknown], I would also assume that Lucy has died.
The state of Virginia kept birth and death records from 1853 to 1896 when they stopped recording to save money. I believe they restarted registering births and deaths about 1911. I may be off in the year of beginning to record again.
Because the census for 1910 listed Mary as Doc's wife, we should know that Lucy has died sometime in the past 9 or 10 years, or more unlikely, she may have divorced. I doubt that she divorced, but if she did die, there is no state death record for that time period. Divorces are a matter of record and could be located.
May I suggest that you have someone look into Volume 3 and Volume 4 of Buckingham Burials, authored by Janice J. R. Hull? I have Volumes 1 and 2, and none of your family are listed. Lucy Wise may be listed in volume 3 or 4, as well as more of that family. That would be so nice!
Finding Lucy's maiden name should be as simple as having someone look at the Marriage Register located at the Courthouse in Buckingham. All years should be checked. The County Clerk's office might be willing to do the lookup for a fee.
If you know what religion Doc and Lucy practiced, the churches of that denomination within the Maysville Enumeration District could be of great help with dates for baptism, funerals, marriages.
Good luck with your search. Research into families of color can be very difficult, if not impossible. But finding our ancestors when we can is very rewarding.