I broke up with my boyfriend by text message, but he kept silent, didn't return messages or answer the phone, and just disappeared. ...

There are many possibilities. Your boyfriend may not want to accept this reality, so he dare not face you again. Or maybe your boyfriend is male chauvinist, thinking that only he can dump you and you can't break up with him, so he ignores you. In other words, he had anticipated the ending, so he accepted it silently.

As the saying goes, if you want to break up, please be formal, whether in person or by phone. It's just a text message to say goodbye. It's not important. Maybe you are just angry for a moment, but when a man lets go of this relationship, you can't get it back.