You guys are missing this part. The dudes kicked the hole in and spoiled his grave days before. I don’t think it was meant for the ex and was meant for JD. She could have very well been brought there, when KM found it spoiled:
“Six days before the May 24 murder, two club members came upon the “disturbed ground” of the would-be human grave, though they shrugged it off at the time because they weren’t aware of any missing people, and left after kicking around some debris so that no one would fall into the hole, the affidavit said.”