[byteface]

Dogs are ridiculously good at intuition, reading body language and hearing. My dog can hear me put my socks on when i'm in my bedroom and she's in the kitchen. It can seem they are psychic. They can sense when I'm acting with intentions and what those intentions are. The dog might have sensed you noticing your friend from a subtle change in your heartbeat or breathing.

[fractallyte]

Yep, I commented below - these are very subtle signals that we're not aware of, but they can't be dismissed either.