Short story about a man filling gas on a planet where aliens used to live

So there's a population of humans living on a planet in space (I forgot the name of the planet). There's this guy filling up gas and he's late for a party (if I remember correctly). He spots a alien in the distance (I think there was a war and the humans killed them all). He follows the alien, not knowing its a ghost. Alien takes him to alien burial site or where it died but guy sees what the life of aliens looked like before they were killed and hes amazed how wonderful it was.

That's the jist of it. If anyone can tell me the name or author of the short story, that would save me a lot of head scratching. Thanks.