Unless the wind swirled and they got a whiff of you then they might be spooked by a coyote or something.
Kinda funny story, my wife gets up before me and let's the dogs out in the mornings. She came in the other morning and said there was some deer in the yard and they were blowing at each other. I said no they were blowing at you and not each other lol.
No telling. I have watched does blow when young bucks try to chase them when it was way too early. Have heard deer blow upwind of me when I knew they didn't see or hear me, then later had a coyote come through. Then there have been times I have been watching deer and all of a sudden old doe starts blowing for no apparent reason. Watching body language in one situation I knew it wasn't me because she was watching down the hill away from me.
I can't count how many times I've heard deer blowing and watched other deer around have zero interest in what she's doing. They don't even stop feeding to lift their heads.