I'm sorry, I guess I don't see the issue. I love Trader Joe's, but if we've gotten a crap product, we've let them know. You don't buy from the creamery directly, right? So, my suggestion would be to go the store where you bought the milk. Most companies want to know - better this, than somewhere downstream, your local TV station, the BBC global news, the interstellar gossip rag.... You know?
I am not sure where this notion of "alerting the authorities" arises, as I'm certainly not suggesting that, and if that is what was inferred, let me be clear by saying I am not suggesting you try to bring down the company. I just know if it were me, and I had what looks like a heart fluke in my milk, I'd like to know if it's well, a heart fluke, snail poop, a hedgehog hair, or something less, nasty. And since I don't have the means to determine that, I'd want to take it to wherever I could find out. Not as a punitive thing, but to simply find out. And if it is a post-pasteurization issue, as I suggested, then that really is a serious breakdown in their SOP, and they need to know.
I sure as heck wouldn't use it, without knowing what I'm dealing with. Again, that's just me, my $0.02. Do what you want, buddy.