Many many years ago I was working security. One Saturday a Police officer asked if he could come into the guard shack where I was working. He explained that they were doing a training exercise with a new tracking dog, and could I allow the person being tracked to hide in the shack. I wanted to see how this worked, and allowed it. The cop radioed that it would be OK. Told me that the cop would be coming from the right, and crossing the road several times.
I watched the officer cross the road, and come into the guard shack. I showed him to a place where he could sit out of sight. he radioed that he was ready, I then watched the dog follow his exact path directly to the guard shack, and right to him.
These dogs are truly amazing. If they claim they have trained a dog to sniff out storage devices I believe them.