I didn't find Luke in Ancestry nor in FamilySearch except for the 1910 Jackson Co. GA Census.
Was he mentioned in John Henry's obituary?
He might have continued to live in Jackson County. The Jackson County Historical Society, www.facebook.com/jacksoncountyhistoricalsocietyofga/
appears to have their historical records at the Maysville Public Library. You can contact them to see if they'll do a lookup.
I suspect that Sallie died there as well. Georgia death certificates don't start until about 1919 so they may have indexed obituaries and cemetery inventories. Successful Searching!