Firefox doesn't store passwords in cookies, it stores them in Saved Passwords. Try checking there. Is this the form that you used to try to recover your password? The one that gets to your secret question and secondary address?
https://www.google.com/accounts/Forg...=mail&fpOnly=1
Have you ever used an email client like Thunderbird or Outlook to access your mail via POP or IMAP? If so, your password will be stored there in the options area for Thunderbird. For Outlook, Outlook Express and Windows Live Mail you will have to look for it.
Hacking into a Gmail account? You only get so many password entry attempts and once that number is reached your account is locked. From my experience, the counter on failed login attempts isn't reset until you log in successfully again. There is no firm answer on the number of failed attempts that it takes to get your account locked, but you say they have already told you that they cannot verify that you own the account. You won't get it back if (when) a hacker gets it locked for you.