I don't know if I will be able to answer your question or not, or if you have since found what you are looking for.I have done considerable research in cemetaries in OK and there is no central place for plot/plat maps to be kept.
I have found these to be kept by any of the following: individuals living in the town, the county clerk's office, a funeral home in the area, the city administration, the water department, the police department, the individual who maintains the cemetery,etc., etc. the list goes on.
The Milo cemetery is described as:MILO CEMETERY is the cemetery for the city of Milo. It is on the north side of highway 53 in Range 1W, Township 2S, Section 32.
Since the Milo cemetery is for the town of Milo, I would suggest you contact the city offices of Milo and simply ask if they can advise you who has the plat/plot maps to show where people are buried.If that doesn't find the answer for you, if there is a funeral home in Milo, contact them - they should be able to tell you who has the plat/lot maps.