OK, I gotta try to remember everything I wanted to post. I was trying to catch up on the thread before actually posting anything.
On the dog: most of the articles make mention that it was a small dog. If the family was doing any hiking/walking, they may have left the dog in the truck because it would be too much for him. As for leaving him to protect the money, I doubt it, if he was a small dog he wouldn't be TOO much protection.
On the cash: As other poster's mentioned, I can't see ANY reason for bringing cash to purchase land. I don't think it would be legal, and even if it was, it would just be asking for trouble and problems. It would be SO much safer to make the transaction with a personal or cashier's check or some other non-cash form.
On the cellphones: It may be as others theorized, that there was no service in the area. However, I NEVER go ANYWHERE without my cellphone. I grew up in Utah and still visit often. And even when I go camping etc, I take my phone. You never know when you might need it, and you MIGHT get reception. Although I don't suspect everyone thinks on those same lines.
If this was a drug deal of some sort, I don't understand why they would bring their daughter.
I live in the Dallas area and my fiance's family is from Okmulgee, OK. It has rained here in N.Texas and also in most of Oklahoma almost non-stop for the last 50 days or so. Maybe 10 total dry days in that time. In fact, I was just speaking with my FIL to be (he visited us last night) and we were talking about how much rain they've gotten in Oklahoma. So yes, it sounds like scent dogs will not be of much use in this case.
Like many others, this case is baffling to me.