Hmmm... but why should somebody even know that B3D used FMOD?
Right, but as the old adage goes, "ignorance of the law is no defense". You may ( or may not ) have a case against the person who didn't warn you about the usage of FMod, but the developer of FMod would still have a case against you. If you lost the case against him, it would be up to you to take a case for that amount out against the person who you felt hadn't warned you.