Thanks for the reply,
I recently inherited my late cousins family history files. Amongst the papers were photostat copies of pages of a book "Petersham Cemetery" by Kevin Quinlan. The pages tell the story of the history of the cemetery, there is a page of References, which includes
"St Thomas a"Becket's Churchyard, Lewisham NSW", transcription of remaining headstones by Errol Lea-Scarlett on 25.4.1955. Society of Australian Genealogists (SAG) Primary records 4/6232 (copy in Marrickville Library, Local Studies Section).
There is also a page which appears to be from a index of burials at Petersham/ Lewisham. which include the names of my G G G Grandmother Honora Teresa Gahan who died in May 1871, and her daughter Catherine Thomas died 1872, and indicate there was a headstone recorded in Mr Lea-Scarletts book. I have been in contact with Marrickville Library and they have no record of Mr Lea-Scarlett book,so I though I would try Rootschat as the resources of the Chatters is unbelievable. Before I put the post up I tried Mr Google, and could find no reference to this publication. My next step will be to contact SAG. I would like to find out if the book gives any other description of the headstone.
I think my cousin must have obtained the photostat pages from Burwood NSW Library, they indicate that The Burwood-Drummoyne and District Family History Group where involved on the project.
This is my first confirmation that there was in fact a headstone on the grave. I have always been told that all graves where moved when the Rail line was widened, I went to Botany and Rookwood back in the 1980's with no luck. Goodness knows how long my cousin had the pages. Thankfully her family passed them on to me, and did not bin them. Sorry for the long story. Regards Cass