The plain question
Most slips don't matter enough to check. The message will be answered, the roundabout is gone, the email was just an email. The three causes are enough, and the charge goes back to being a guess, and you move on. But sometimes the slip matters. The friend's silence is the fourth in a row. The colleague's interruptions are costing you standing. The brother's forgetting has a history. For those, the three causes aren't enough, because you need to know, and the only way to know is to ask.
The plain question is one sentence, asked of the person, about the act, without the charge attached. "I noticed you've gone quiet, is everything all right?" "Did you mean to cut in there, or had I run on?" "It felt a bit sharp when you didn't say hello in that email, was that just speed?" Notice what the sentences do. They name the act, they offer the innocent cause, and they leave room for the answer to be anything. What they don't do is say "why did you ignore me", which isn't a question. It's the charge with a question mark on it, and it gets answered with defence, not information.
The plain question feels risky, and it's worth saying why. Asking exposes that you noticed, and that it mattered, and the charge was partly a way of not having to admit either. But consider what you're protecting. You already look like you noticed, because you've been cool since Monday. Asking replaces a coolness nobody understands with a question anyone can answer.
And the answers are almost always a Tuesday. "Sorry, I saw it in the shop and it went out of my head." "Did I? I didn't notice, sorry, I'd been waiting to say that for ages." "No, I write all my emails like that, I'm told I should stop." Now and then the answer is something else. "Actually I've been a bit hurt since the thing at Easter." That's the pattern turning out to be real, and it's the best possible outcome, because now it's out and can be dealt with, instead of being a charge on your side and a puzzle on theirs. Either way you know. The charge never gets you that.