I would likely assume I am the only one seeing the cow, because it would be an unusual occurrence. Just in case though, I wouldn't try to park there. I would park somewhere where I could still see the cow, and try to ascertain if other people are also seeing it. If they were, then I guess I'd be looking up the number for animal control to see if someone could come get it before it gets hit by a car. I might be inclined to offer it water if I could find a suitable container. I might name it.