I was the passenger in a friend's car and we were heading through town in a NNE direction at about 6:30pm M.S.T., There is a plateau on the edge of town which was directly in front of us about .5 miles away with a ridge which rises up behind it. Directly ahead of us in the night sky I witnessed a bright white light in a stationary position. I thought it might be a plane (which is rare to have planes flying over town especially at night) and I knew it couldn't be a reflection from the sun as the full moon had just risen behind it. I rolled the window down to get a better look at it and to see if I could hear any sound from it and right then we came to a stop light so I was able to point it out to my friend who was driving. We watched the light together for about 20 seconds and then it just disappeared.I thought I might be able to distinguish some sort of a shape of the object because of the back lighting from the full moon, but the object was completely gone. There we no other aircraft in the sky that we could see.We were both astonished at what we saw and then didn't see.