Create a new blockchain.info account and restore it from your wallet backup. Next time write down the authenticator's secret key.
Thanks for the advice. Does restoring from a backup restore the wallet from where it was when the backup was taken, or does it look at the blockchain and restore the entire wallet? The backups I have weren't necessarily taken right before I lost access.
Bitcoins aren't stored in your wallet. The wallet is simply a collection of public/private keys. Once the keys are restored, the blockchain will be scanned to find out the total of the unspent outputs that equal your balance. The restored private key will give you the ability to spend them.