However, if you happen to have generated the private keys to the associated bitcoin address(es) BEFORE you lose your passphrase, you can either
1) "sweep" that address from another Counterparty wallet
2) import that (Counterparty) bitcoin address into another "open" wallet. Most open wallets aren't Counterparty-aware by default. Some wallets can be made to be. However your assets will be there and not lost - again, if you have the private key. Non-Bitcoin assets will only be accessible - and therefore manageable - from Counterparty-aware wallets.
Between either your 1) wallet passphrase or 2) your Counterparty wallet address(es)' associated private key(s), you can regain access to your Counterparty wallet assets.
If you are reading this BEFORE you actually lose your passphrase, you may want to consider generating your private key and storing it someplace (offline, probably written or printed, then stored in a "safe" place.)