I have done some further digging and uncovered some things. I contacted Mill Springs Museum and they said it's unlikely that he would be buried there. Many sources from early genealogy state national cemetery in Bowling Green...likely Fairview Cemetery. I contacted City of Bowling Green and they think based on dates and what I told them that he could be buried in Fairview. They said 200 soldiers were moved there from a mass grave near the WKU campus. She said a lot of those soldiers died of disease. I think people list Bell Station as a death place because of the findagrave location initially listed. Based on everything I know now. I find it highly unlikely he was buried in Mill Springs Cemetery.

My question now is how can I find out if Marmadukes 18th Arkansas Regiment was around Bowling Green in January 1862?

Also, where did you find a picture of him? I'm guessing from ancestry.com. I uploaded a picture of him that only a few copies exist to my knowledge. My tree is the most complete on John Robert Castleberry that I've seen thus far.