Thank you so much for the response! I had debated about whether Myrtle were possibly buried in the James Watkins Cemetery, but I wasn't sure of death dates for his children and thus of who would have most likely been place there in the correct span of time. It's reassuring to me that you feel it's a distinct possibility, and with good reason. However, of course this means that if this is the case, the grave cannot aid me in finding out anything about Myrtle -- versus if she were buried with her parents, we'd finally have some names of her family members. So that's a real shame there, in that respect.
I suppose my next area of inquiry would be whether there are possibly a significant number of Thompsons buried somewhere else in the county, if not at least in Arkansas.
This is a wonderful outlet for research help-- thank you so much for making such an effort to be of aid! No doubt you know that it's not easy to access cemetery internment lists on the Web; and I've certainly tried it that way in order to try to at least get a birth and death date for Myrtle, who is my great-great-grandmother. There are multiple deaths of wives and mothers and lots of holes and absent fathers on this particular side of my family.