Were it not for her vehicle getting an unexpected flat tire, this case would've been TOTALLY perplexing. If things had gone per plan, her car would have been found two or three towns over in an attempt to shift the search efforts to an entirely different region of the State.
The car being found abandoned where it was is the biggest indicator to me that she is still somewhere in the Bardstown vicinity. Somebody was in the process of trying to stage her disappearance when the tire went flat. In my opinion, relocating the car in order to shift the focus of the upcoming investigation was the last part of the overall plan. The most glaring question in my mind is how did the driver of her car get back to Bardstown ? If the car had been successfully moved to a distant town or locale, how did the driver plan on getting back home ? I'm sure there is an answer to those two questions, it just isn't obvious to us. Because of those two questions, that's why I believe two people had to have been involved in the cover-up.
Crystal told her family and friends that if anything ever happened to her, to look at BH as the prime suspect. She told them that for a reason. Maybe it was intuition or maybe he openly bragged about being able to make people disappear and commit the "perfect" crime, either way I think she believed him. He may have gone as far as to tell her exactly how he would do it. With all the turmoil and infidelity in their relationship, it's impossible to know if this event was sparked by something that happened during the last weekend they were alone, or if it had been planned out in advance while waiting for the opportune time to pull it off without being detected.
Either way, it appears that there were no bread crumbs left to follow with the exception of the the flat tire on the car. No cell phone tracking, no surveillance videos, no eye witnesses that saw anything unusual,..........nothing.
My only suggestion at this point would be for LE to dig into his background and try to figure out what books he's read recently, what his internet searches show (which were probably all deleted by now), and what his favorite movies are. He had to have gotten the idea from somewhere on how to pull off the perfect crime and how to behave afterwards. That information may be found right there within the walls of his home.
Interviewing his close buddies and other LE contacts he may have had in regards to conversations about such things would also be advisable, but I doubt it is going to yield results. Most likely the only "buddy" he would have talked to about it is a sibling of his that used to live on the same street, just a few houses down.