Ancestry.com is not great for researching slaves. The Slave Schedules are on the site but as you probably know slaves aren't listed by name, just age, gender and color. You may be able to narrow down the slave owners in 1850 and 1860 by his age and color in Pike County.
Have you checked www.familysearch.org
? On familysearch.org, you may be able to use it to look up wills and deeds to find the slave owner. Also you may want to trace Sol's children in 1870 in the US Census, if he died before 1870.