Is it possible for a catalytic converter to go "bad" four days after passing a state emissions test?

I recently passed state emissions testing... Exactly four days later, my SES light came on revealing code: P0430 Catalyst System Efficiency below threshold Bank 2. Now I am told I need a new catalytic converter. How is this possible? Do catalytic converters just go bad one day? How can it pass one day and be dead the next?