I had a cat. The cat would do stupid stuff while I was away and when I'd get home I'd get angry and smack the cat with a newspaper. Then someone told me: the cat is like a small kid: if you punish it after more than 5 minutes, it doesn't associate the punishment with the "crime".

People outside your team won't understand your reasoning. They'll see code working one day and a random failure a long time after that, which might or might not be related to the previously working code. They're just like my cat.

If you want to act for "shitty code", act before it's in production. Afterwards it's very hard to dislodge. And even harder to pinpoint the blame, as the author will definitely protect his back, ethically or not.

I'd take the experience as a lesson in human interactions :)