Cristian there is no records of CS6 being registered under the current Adobe ID. Did you purchase the educational version of CS6? If so then you can locate your product code and follow the process listed at http://forums.adobe.com/message/4635085#4635085 to obtain your serial number.
If you had a serial number previously then that would indicate that you have already gone through the eligibility process. When you go to the Identit-e site and enter your product code it will then provide you with the serial number. I would also encourage you to register that serial number under your account at http://www.adobe.com/ in case you need the serial number again in the future.