There are 3 elements needed to be successful long term in Canine Scent Detection.
The dog needs to know what scent they are looking for.
The dog needs to want and know how to search.
The dog needs to be able to clearly tell you it has found it.
You would think these are obvious but too often we get bogged down in teaching one of these skill that the other 2 are forgotten.
Most often we worry about the dog "identifying the scent". We set up hide after hide moving the scent around, maybe adding distractions and guiding the dog past the set up until they find it. Really this is teaching the dog which scent pays. We think we are teaching them to search, but they are really just learning 'yes', or 'no'. Is the scent at this object or is it not.
Searching is a separate skill not taught at the boxes or in a typical class set up. .Class settings have to be controlled. There are many dogs in the room, and instructors have many classes and reuse spaces often. They need to be able to remove and clean the area the scent was hidden, so most hides in classes are placed in something. This means that all of those hides have visual cues. A hide is always in something that the dog can see creating the expectation that all hides have a visual element. You, the handler, also get into a routine of going from object to object and asking the dog "is it there?"
So, how can you teach a dog to search? This is where your homework comes in. They need to be taught to use the scent cone and follow it to source despite any plan we may have of how they should search. For a dog to learn to search they need to be given free reign to explore the area without interference. This is how they build drive and determination. We have to teach them to follow scent and not trust their eyes only. They need to be given hides that challenge them to use their nose, not just go from object to object. Sport detection dogs need to practice hides placed in a random place without any visual clues. Try throwing the hide in the grass or place it in a crack on the wall, sit down and tell them to search. Can they still find it. Will they still even search?
A dog that is never taught a container search will still be able to find a scent in a container, but a dog that has never been taught to follow a cone without visual clues will not be able to find a scent in the sand.
The third piece needed is a clear way for your dog to tell you they have found the hide. I have addressed this issue in another post; Why I want more then a Freeze and Stare