If you are not receiving an email when you submit a password reset request for a Diablo 2 battle.net account, these are the possible reasons I can think of why:
1: Your account was never set up with a recovery email address. Normally when you create a new account, you are prompted to enter an email address for recovery purposes. If you skipped this, then the account was not set up with an email.
2: The email may be going to your spam folder.
3: If it’s been over 3 months since you last played, your account has expired and the account name may have been taken over by someone else. Anyone else creating a new account can choose the same account name as an expired account, which effectively overwrites the expired account.
4: You set up the account recovery email with a different email address.
5: You’re not typing the account name correctly.
Beyond the email recovery feature, Blizzard will not assist in the recovery of lost accounts. A big reason is because there are a bunch of greedy players that would love to have a way to steal others accounts.