"If they cared they'd have replied"
The unanswered message is the slip people carry longest, so it deserves its own chapter. The charge runs like this. They've read it, they've had two days, replying takes ten seconds, and they haven't. So the ten seconds weren't worth spending on you. It's clean, and it's the kind of reasoning that would hold up in a meeting.
Here's the unseen half. They read it on a phone while standing in a shop, intending to reply properly when they'd got home. At home there was a child, a meal and a call from their mother. By the time they'd thought of it again it was a day old, and now the reply needs an apology at the front, and the apology needs a reason, and the reason is that they forgot, which is embarrassing, so it needs another day to become something they can say lightly. Meanwhile the message has gone under a stack of others. None of this is about you. It's about how messages behave once they've been read and not answered, and you know this because you have a message like that yourself, right now, from someone you like.
The ten-seconds argument is the tell. It's true that a reply takes ten seconds. It's also true that the ten seconds have to happen at a moment when they remember, have their phone, aren't mid-something and have the reply in mind. The charge treats a two-day silence as two days of choosing not to. It was more likely two days of not being reminded. Absence of a reply isn't a message. It's an absence.
And there's the question of what "caring" would look like if it were measured honestly. Not the speed of one reply. The last year. Did they turn up, ask about the thing, remember what mattered, come when you needed them? If the answer is yes, one silent Tuesday doesn't overturn it, and reading it as though it did is choosing the smallest sample you can find. If the answer across the year is no, that's real, and chapter 7 is for it. But it won't be this message that told you.