Stealer is a describing verb, but still a description of the action taken, not of the person itself. A person who steals is most commonly known as a burglar, thief, con artist, criminal, scheister, ne'er-do-well, misanthrope, and many others. Never have I heard anyone use the term "stealer" until hip hop became popular and we all know how illiterate those people are. Stereotypical, but true.