Your Passive Rewards Account is custodial (unlike the funds you store in your DeFi Wallet, which is non-custodial), so it is not backed up by your wallet's backup phrase.
However, your Passive Rewards Account is associated with your identity profile. Thus, if you have lost your password, you can recover your wallet here using your 12 words recovery phrase and proceed with account verification again in order to access your custodial funds, including funds in your Passive Rewards Account.
If you have lost your password and your recovery phrase, you will still be able to recover your custodial funds, including funds in your Passive Rewards Account, however, the funds held in your DeFi Wallet will be lost. For more information about account recovery, please check this support article.
Please note: the Passive Rewards Account is not a bank deposit and is not backed by any governmental deposit protection regime. Your rights in connection with the Rewards Account are governed by the contractual relationship you enter into with Blockchain.com via the User Agreement.