Well, not really forgotten, the thing is that I was unable to access to recovery or boot to another disk (like the recovery in time machine disks) because the Mac have the firmware password.
Why a firmware password?. Well, to protect your machine in case of being stolen/lost. The password will stop the boot process if the boot disk is not the one that was present when the password was set. Also stop booting to recovery/USB/Super Drive.
This firmware plus FileVault (disk encryption) will prevent getting your data or use your mac without permission.