Yes they do know us. BPs' heat sensors are tied into their optic nerve; they can see our heat signatures and as predators I'm sure they are able to quickly learn and recognize very slight differences.
What we might look like to a BP:



I've had him draped around my neck while talking and he squeezed a bit to feel the vocal chords moving, so I think he recognizes the sound of my voice (or else he was trying to figure out if he could kill and eat me LOL).