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Forget what you learned in college. "If X happens, then I must have done something wrong". Nonsense. If X happens, then X happens, that's all. Don't let anyone tell you that everything is your fault. If you send a message and I don't reply, the only valid conclusion is that I didn't reply. Anything else is speculation.

I send a message "I'll see you tomorrow at 13:30". If I see that you read the message, that's my reply. That's all I need to know. In many cases, it is understood that there is no need to reply to the message - unless you disagree, for example if you can't make the meeting.

And if I send a message "I'd like to see you tomorrow, what's a good time for you", and I don't get a reply, then I got a reply, and the reply is that you don't have time or don't want to meet.

And people are busy. Yes, text messages get ignored, because people are busy, because they can't be bothered at the minute, because six hours later the message is forgotten. There is no need to worry if you don't get a reply. That's how text messages work. You send them out, they tell people what you wanted to say, and sometimes you get a reply.

PS. If you send me a message "How was your day", that will be ignored, unless I'm sitting on the sofa, totally bored, and that is a very rare situation. (And unless you're my wife, and we are away from each other for some reason).

PS. I'd recommend to anyone, if you feel that somebody upset you, don't just ignore them. Either get over it, or tell them that they have upset you. In the unlikely event that this is what happened to OP, he would have felt a lot better being told "you upset me, and I'm not talking to you".

PS. How do you know the message was read? It is "marked as read", which means your computer or phone believes for some reason that it is read, but that doesn't mean it was actually read.