Most Helpful Guy
Often children display genuine feelings that adults have been taught to try not to feel. I have a feeling that may have happened right here with you when looking for advice based on what other people do. Ideally you two would communicate well but none of us know why he didn't talk to you and what you're feeling. Saying not speaking to someone is childish is a really broad statement that I didn't think is good advice for everyone.1
Most Helpful Girl
First understand why he is doing it? Did something happen between you two? Arguments or did you behave in some sort of way that caused his mind to think twice about you?
Because this can happen, and they sometimes need a time out and to see where they stand.
If not, talk to him, but not through text, face to face conversations work miracles if they are made correctly.
Ask him what is wrong and what could be done to improve :)