dawalk on Family Tree Circles

I am trying to establish the details of the father of Thomas WALKER born 1820 in Messingham Lincolnshire, according to Census details. I have established that his fathers name was William and that he had died prior to 1842 when Thomas married, William is shown as deceased and occupation as farmer, on the marriage certificate. I have searched parish records for Messingham but cannot find the birth of Thomas recorded, there is however a William Walker who is recorded as the father of other children in Messingham at that time, no occupation shown. The mystery is if this is the father of Thomas why was the birth not recorded. Can any body help.