Fun fact: according to our models the photon doesn’t exactly travel in a straight line and hit the eye of the cow. It’s a probability wave that spreads out spherically across an astronomical range. It might as well “hit” Mars instead of the Earth. What actually happens is that the huge wave randomly interacts with the eye of the cow. At that time the probability collapses into a certainty (the photon), making it impossible for the wave to interact with anything elsewhere in the universe.

Edit: or if you subscribe to the many-worlds interpretation, the wave interacts with both Mars and the Earth. When the wave reaches the eye of the cow, a new series of waves ripple out. They contain the effects of a photon interaction, but the original (standing) wave before the interaction also remains. We can make a slice of the multiverse in which the cow’s brain perceives the photon, and another slice in which there was no interaction and the cow didn’t see it. Because of how consciousness is tied to a single chain of events, the cow as a matter of experience doesn’t both see and not see the photon. Rather it’s as if there are two separate experiences that exist independent of each other.