Is it possible that the registers for Penycae parish have not yet been made available online? This is what FamilySearch says:
The following Penycae Parish Registers have been deposited at the Denbighshire Records Office in Ruthin:
Baptisms 1880 - 1919
Marriages: 1880 - 1971
Burials 1881 - 1952
The Clwyd Family History Society have published one volume of the Penycae parish registers.
There are no official records available on the IGI for Penycae parish.
Perhaps worth contacting the Records Office? See what other responses you get, as I have no experience researching in Wales, but it may be the best option.
Queenie

EDIT: I see your other thread has identified the cemetery.