Well..... In the first place, deer are deer. They are smart!! They spend their entire lives, trying to stay alive!!!
However... Like they used to say about Wild Turkeys, If they see you move, they're gone!!! True!!! But... If a turkey spent his entire life "spooking" every time something moved, It'd starve to death!!!
Deer are much the same. They have a food source, water source, bedding areas, trails etc.... If they get spooked, it's only for awhile, and if whatever spooked them doesn't kill them, they soon go back about their business of staying alive. They have 3 defense mechanisms. Their eyes, ears, and nose.
We hunt mountain deer. The wind changes direction about every 10 minutes. You would go crazy trying to "hunt the wind" up on the mountain. I have had deer that CERTAINLY winded me, walk up within yards of me, and then walk past me and browes off into the laurel, because I set completely still and avoided eye contact.
If a deer is in a field to eat and get spooked out, it is NOT going to go hungry because something spooked it!!!
As soon as it's senses tell it that it's "all clear" it will return. It's hungry!!!
A deer trying to stay alive, lives in the moment. They do not have the "reasoning power" that humans do to think about the future.