In any case, I read this as the notice that payment was required is what got lost, not the payment itself.
Let me tell you what I hear as a business person if you tell me my letter to you was misdelivered: "My mail delivery is unreliable so it's your problem."
Well, no, you didn't tell me it was unreliable, so I couldn't adjust my risk perception or take special precautions. And if you ever want to do business with me again, you're going to come in and execute the transaction on site and not leave with the goods until the bank confirms it's cleared.
On top of which, most billing contracts specify that payment is due whether or not you were notified. You are supposed to keep track, too.
And yes, this is okay, because until we have a proper socialist system, it is, in fact, our responsibility to pay our debts. Don't like it? Don't incur debts.
Anyway, we’re back to making it the responsibility of the customer with a thousand more important things to think about, rather than of the business that’s dedicated to the stuff.
And if you think it should be that way, great. But it’s obvious to me that it is that way because of the power imbalance, not because it’s right.
If you don’t make payments as agreed, your credit score goes down. If you do, it goes up, and will soon recover from the perfectly reasonable dip it took from your mistake. It’s pretty simple.