Pamela, My computer just went haywire and I lost the message i was typing to you! Boo!! Anyhow, I didn't find them in my books. my suggestion would be to write to the Caldwell Couty courthouse 100 E. Market St. princeton, Ky 42445 See if they have a marriage record for them. Be sure to include a SASE so they can respond easily.
I found them on the 1860 census living in Alexandria, LA with all of the children being born in KY so it's a good bet they married in Caldwell. The 1850 census has Dora listed as Rhoda Pickett with 3 children. It also has them listed as mulato but never again. In 1870 Hayden is gone and Sedora is living with daughters Laura F. and Henry Ann.
Did Hayden serve in the Civil war? If he fought for the Union and he or Sedora filed for a pension there could be some valuable info in the pension file.