Since there are recent burials in this cemetery it seems that someone somewhere must have a record of the plots and who is buried in each. I would love to get my hands on this and find out where Isaac and Lydia are buried. Adding a memorial headstone to their final resting places would definitely be something I'd like to do. It's a very small cemetery, about 150 tombstones and I suspect that Isaac and Lydia, who died in 1904 and 1917 respectively, are in the northwest corner where the earlier stones are found.
Isaac Vollick's obituary reads
Elmavale Lance, Wed. March 30, 1904 page 9 "Hillsdale Notes": "Isaac Vollick an aged resident, died at his home on 5th concession of Flos last Friday evening at the ripe old age of 73. The remains of this pioneer settler were interred in the Methodist burying ground Monday morning. Rev. James Skene conducted the burial service."
Lydia (Jamieson) Vollick's burial record was found in the only known church record book which covers only a few years:
Register of Hillsdale Methodist Church: Deaths: Lydia Vollick; 80 yrs; born Wentworth County, Ontario in 1837; died Oct. 15, 1917; gangrene; buried Oct. 16, 1917; buried Hillsdale; Minister Chas. C. Fry
Here is today's Cemetery Walk on Olive Tree Genealogy Channel on Youtube