People think this is a "clue," so I tried to analyze this "clue."
The fact that the dog sniffed something might be a clue,
but the fact that Alucard transformed into something resembling a dog, and that Neira has it in her signature, has nothing to do with the clue.
Unless Neira is the detective who discovered this clue :D
So, we have another nonsensical thing in your interpretation.