No code exists that says 'clogged cat causing high air/fuel mix'.
A melted/clogged cat will generally make the car run like crap... low power, missing all over the place, etc. If it's a P0420, your cat could indeed be done for, even if it's not clogged, or it could be as simple as the rear O2 sensor. If it smells like raw gas, it's possible there's a problem with your front O2 sensor and/or its wiring that's making the car think it's running lean, even when it's rich as hell. That'll usually be acommpanied by a code for the front O2 sensor and a lean mixture code.