Even with a positive hit, you must still have a specimen to begin treatment. The dog handler should produce a specimen to confirm the dogs behavior response. If the inspector cannot produce a bed bug, it could be a false positive. Or, the dog could just be having an off day. Will they come back and do another walk through. This is fair because if there is a positive "hit" but no specimen found, you are still in the dark about whether what's biting you is bed bugs. If you aren't offered this, ask if it is part of the service. You can let them know that you expect it.