It is too late now, but this is what our family did to protect a plot.  We bought two plots near my FIL and MIL, it was their desire for all of to be buried together, but there was not room where they were buried because they dug their holes too far apart.  We learned somone was going to sell some plots just in front of them, and purchased them.  Realizing something like you experienced might happen, we purchased stones just like MIL and FIL, and put them in our plots.  My wife says every memorial day she had no idea she would have to weed eat around her own stone.


This doesn't help the original poster, but I post it in case someone else might experience the same problem.  Besides marking the locations, I figure inflation in stones will make the early purchase an good investment.  Our names are engraved, all someone needs to do is cut the date of death, because I cannot know that at this time.  If I never gets cut, it won't matter to me anyway.