I shot a doe once that stood and blew and stomp the ground at me for what seemed like 5 minutes. My back was to her when I heard her. She apparently smelled me, or saw enough of me that it made her nervous. I turned my head and saw her about 25-30 yards behind me. She'd blow/snort while looking right at me, then she'd stomp the ground with her front leg once or twice and then hold still and just stare for several seconds. Every now and again she'd drop her head to where she couldn't see me, and I'd turn around a little and bring the gun up and around a little bit and I'd freeze when she raised her head to look at me again. She did this 3-4 times before I'd managed to turn around and shoulder me rifle. She was in the frozen/staring phase when I shot her dead. I think that she had no idea what I was, and was trying to scare me into moving so she could figure out what I was and if I was a threat.
If you get busted, a lot of times the only was you know is that you hear that blowing sound as they run away, but there have been times I never saw the deer that made the sound.
Mike