Normally employment agreements in China include a probationary period where you can quit without notice. Since you quit so early one, did you even have a work permit and residence permit (this normally takes two weeks to get processed). I know that many teachers are brought into China on business or tourist visas which really do not allow you to work. I'm with Moondog here, this sounds like a case for a visa agency to review. Anyway, if there were to be an issue, I would think getting a new passport would fix this?