Heather,I finally found that marriage in south australia
her surname is spelt slightly differently
Digger - South Australian Marriages, Registrations 1842-1916
Groom: FAWCKNER Given names: Charles John Bride: HERRAMAN Given names: Susannah Date: 1872-04-30 Groom Age: 24 Status: Single Groom's Father: Robert FAWCKNER Bride Age: 28 Status: Single Bride's Father: James HERRAMAN Place: [unrecorded] Adelaide District: Ade Book/Page: 91/352
If they were born overseas have you checked to see if they returned?