If you look at what it takes to satisfy AHIMA's requirements for the CCS exam, the requirements are tough. I don't think you do that by self-study alone, so you would not be eligible from the self-study. You would only be eligible because of past work experience actually doing medical coding, which employers don't normally allow a non-credentialed person to do. You definitely need to come up with a better explanation of how you accomplished that CCS, because the story the way you told it will keep you from being considered.