2FA can be reset by inputting your Wallet ID and Email Address in to this form: https://login.blockchain.com/#/reset-2fa

If you forget your password, then they state that they have no way of accessing customers' wallets and no way of recovering lost coins. If this is to be believed, then the accounts will sit dormant forever with the coins essentially "lost" unless someone is able to hack in to them.

However, since they are a closed source third party, we have absolutely no way of knowing if this is true. They may very well be able to access all their customers' accounts if they like, or they may back up seed phrases independently, or they may store passwords in a decryptable format or even in plain text, or any number of other accidental or intentional security flaws. Such are the risks you take using a web wallet.