dogs are not fool proof. We just saw in Blaze Bernstein's case - cadaver dogs were used and didn't find him, though he was right there. It happens. The dogs are a tool but are not foolproof.
That said, I am not sure they were in the Jeep at that location. Hoping for an update soon.
Thats a good point, especially when you factor in weather and how long it took to find the Jeep. With that being said, the police, who are familiar with the K9 process, feel like its reliable enough to publicly announce foul play.