If something had been placed in the dog's way, in a place it wanted to go to, would it indicate that to the trainer?
Not sure what you mean by something placed in the way?
If you mean do physical obstructions cause a working K9 to look over their shoulder and say to their handler, "Really???" then yes, lol.
If they are working a specific scent then they should- and usually do- alert. Because they need extra hands to help them access the more dense source of the scent.