I remember reading a story a few years ago and couldn't afford to get the rest of the series, and since then, it has disappeared off of my kindle. It's a story about a society that treats people with "special abilities" or that look different into a different part of the city and aren't allowed to roam the streets where the "upper class" people live.
Anyhow, the main character is a female, and she is missing an arm. It starts with her and a friend in a club on the other side of the city (the nice side) and a guy notices her missing arm and blurts it out. All hell breaks loose and she and her friend have to book it before the authorities catch them.
Her missing arm is actually because of what she is, but she doesn't know this until she runs back into the guy from the club and he tells her.