Hello Bronwyn
Welcome to Rootschat

Do you know where your GG Grandfather lived in 1861 and the address from the 1869 death certificate? People often walked many miles to work so he may not have lived in Fforestfach. They didn't necessarily attend Church or Chapel in their own Parish either, but freqently walked a few miles to attend one of their chosen denomination. Many Chapels had their own graveyards like Bethlehem and Calfaria, mentioned by bevbee.
Have you found the family on 1861/1871 census? Post any details you have to help narrow down possible burial locations.
Updated: I see from the other post that his name was David Jones so that's nice and easy

I can see David Hosea Jones age 31 and David Howell Jones age 42 in 1869 (Dec Q), and 73 year old David Jones in the following quarter.
Probably found David Hosea Jones, collier, age 22 in 1861, as his father had the same name. Living at Gorse Lane, Swansea (from district 14 description, likely to be in Cwmbwrla/Cockett area. There is Heol-y-gors and Gors Ave on current map. From the nearby properties, it's looks like the part of Gors Lane nearest to Cwmbach Rd which is Cockett area.)
RG9 Piece 4100 Folio 47 Page 57
Kind regards
Morgan