Hi, John - It was nice meeting you at the Roane Co. Gen. Fair in Sept. and leafing through you book on the Sinnett family. I have only a distant connection to the Sinnett's through my Jarvis line. Anyway, I've done some digging and at least found John Sennett [sic] in the 1850 census of Kanawha Co., VA(WV),age 62, no occupation, with three Sennett young men, persumably sons: Able P.age 34, county surveyor, Samuel age 24, farmer and James age 24, farm laborer. Able P. Sennett was still listed in the 1860 census of Kanawha Co. while sons Samuel and Joseph were listed in the Roxalana area of Roane Co. I do not find John S. Patrick or Elizabeth Caldwell Sinnett in any 1860 WV census. Your dates for John: b. 12 Nov 1787 d. 1 Jan 1869.
I did find John Sinnett's, age 71, marriage to Elizabeth Eastridge Caldwell, age 41, from Washington Co., VA., married in Roane Co. 19 Dec 1858. Source: Cochran Pub. 1988, Roane Co. Marriages, p. 6. Record indicates that both were widow/er. She was first married to Andrew Caldwell and they had at least two daughters, Phebe S. who married James B. Groves and Kesiah A. who married Mark Hively, but I do not find any children for her and John Sinnett. I find Elizabeth 1870 census of Roane Co. living with the Groves family, and in 1880 living with the Hively family.
Hope this helps a bit in finding your Sinnett ancestors.