An uncut diamond
Why "uncut diamond"? I've inadvertently posited the idea that no one notices the star because it's dull itself, instead of that the neon lights are bright.
Also, the most important part of a haiku after the syllable count is to make a contrast - haiku traditionally contain a natural image, and some kind of comparison that leads to a new understanding or way of looking at the world. I've missed that altogether in my first drafts.
I consider that I have several opportunities for contrasting images here, even in such a short poem. First, I can compare the star to the lights below. And, if I play it right, I can contrast the quality of the star to the quality of the city's neon.
I decide I can play on the usual impression that neon is a warm kind of light, and give it a more sanitized, cold feel, while brightening up the star, cutting and polishing the diamond, so to speak:
A bright speck diamond
The star is bright, simple, and beautiful, but the cold and busy world below ignores it.
I'd still like to warm up the star a bit, but all in all, I'm happy with my haiku.
A little editing, as you can see, can make a huge difference between a nice idea or image, and knowing that you've actually found a way to communicate that idea.
Writing is a medium of communication, after all, and editing is one of your finest tools to ensure that communication has the effect you intend.