Sometimes when cemeteries were landscaped any gravestones were removed, sometimes any gravestones where buried under the turf. I haven't found any reference to what happened at St Mary's Cemetery Kirkdale. I think unless the land is going to be built on the usual procedure is to leave the contents of graves as they are and bury any gravestones. One of my ancestors is buried in Grimsby, Lincolnshire, England in a cemetery that is now a park. There was a gravestone as I have a copy of the inscription unfortunately the gravestone is now under the turf and the exact location of the grave is unknown. I once walked through part of Lester Gardens it was a bit quiet and secluded. Probably not that safe a place to walk around.
St Mary's Cemetery Kirkdale
"It is now called Lester Gardens in honour of Major Lester who was vicar of St Mary's church for 50 years.
Although the cemetery was called St Mary's, Kirkdale, it was not attached to the church and had no association with it.
First burial 3rd August 1837, final burial 5th November 1898."
(copy and paste this below for a map of the cemetery)