St. Ignatius of Antioch Church only has Mary's burial as being in Olmsted Falls, Ohio. No other information is given.
I have called Chestnut Grove Cemetery in Olmsted Falls and they do not have records for Mary Costello or any Costello.
I have contacted Holy Cross Cemetery (administers St. Mary of the Falls Cemetery in Olmsted Falls) and they said they do not have all the records from the church, and that some of the older records are missing.
I have done a grave by grave search of St. Mary of the Falls Cemetery on Bagley Road and did find a Mary Costello, but this Mary Costello's husband is Dennis, and a son is Timothy Costello. These Costellos I have found in the CPL Necrology file and I find no common ancestor, as of yet.
I am hoping to do further census searches, and I am also going to look at the ledger(s) for Cuyahoga County deaths 1867-1900 at the county archives to possibly find Thomas' death there. I have not done so yet.