while it is true that the way a pigs neck and spine are built it can't tilt its head straight back in any useful amount, a pig lying on its side can easily see sky, that also happens to be the way they sleep and rest, laying on one side. Also the amount that a pig can tilt its head back mixed with the amount that a pig can tilt its eyes up would allow it to see a good portion of the night sky, but a pig laying down under the stars to sleep would see the whole sky with all the stars before it closes its eyes.
This is a myth they can look up