It is frustrating but sometimes you just have to accept that you have a dead end on one line of your tree. I have two similar things on my paternal line. On the certificate for my great grandparents' marriage in 1887 both father's name & occupation columns are blank. The bride's mother never married. The groom's mother married 9 months after he was born and her husband was shown as father to him (and his father as grandfather to him) in the censuses thereafter, the boy using his stepfather/father's surname. However when he married and for following censuses and in life thereafter, he used his mother's maiden name.