Comet shaped object over hills outside of town, silver/reflective, appeared stationary.

I am 20 years old and have never had a UFO experience.  
I was sitting in a parking lot with my significant other and we noticed what looked like a comet hovering above the hills, probably about 50 miles outside of town, to the northwest.  It had a silver hue to it and looked almost like it had a tail, except it was all one object, it seemed like.  It seemed reflective, but the sun was going down, so it was hard to tell.  We had to drive away, but then we came back, and it was gone.  We didn’t see it move at all while we watched it the first time, so it seemed strange that less  than have an hour later it was gone.  We watched the sky for awhile as it got darker, but we never saw it again.