I was disappointed the show wasn't a full hour as well. I believe on Tricia's show tonight, Elaine said he was asked in the past regarding a walk through in the past & he refused LE. Mark shouldn't refuse anything LE asks if he wants to help & if he doesn't, well it doesn't look good to say the least if you want your child back right?
I'm surprised he hasn't been arrested yet as well, but I believe he will. I can see LE saying it was homicide since, he had no method of traveling the road way to the site (it was over 10 + miles), he couldn't climb the steep cliff & if there is proof that his remains had been moved it could only spell "homicide", not too different than finding a person that had say had numerous knife wounds that could not be self-inflicted, but they don't have absolute proof who did it. JMO but his day is coming.
ETA - It's kind of like when they found Caylee Anthony's remains in the garbage bag. At first they didn't know how she died, but they knew she was murdered as Caylee didn't put herself in the bag.