To be fair, Duncan wasn't an expert in the field of the Transcendent, nor was he knowledgeable about disciplines related to dreams and the mind, but he still vaguely judged that the scenery presented on this street should be more than just what Sherry "saw in her dreams."
The murmuring cries for help from the ashes really gave him an uncanny sense of déjà vu—
He thought of the factory, of the people hidden behind curtains, burned to ashes in the fire.
Of course, the ashes in the factory didn't cry out for his help—the ashes conveyed to him a more direct and intense signal: they let him see the "echo" of the fire that happened eleven years ago.
Subconsciously, Duncan believed there was some connection between the ashes on the street in Sherry's dream and those in the factory.