Remember to send me a message before going on a business trip.

According to the information you provided, the boy has gone on a business trip and will inform you when he comes back, which seems to mean that he wants you to be informed when he comes back, perhaps to arrange a meeting or discuss something. He used to calm your temper, but now he is extremely cold to you, which may mean that he has been under great pressure recently, or has some emotional or personal problems to deal with.

However, people's behaviors and reactions will change with time and circumstances, so we can't draw conclusions only based on this information. Here are some possible scenarios:

1. He may be depressed because of work pressure or personal problems, and he is not in the mood to deal with other things.

He may think that you no longer care about his affairs, so he doesn't respond to your emotions as positively as before.

He may think that your relationship has changed, or he may want to keep his distance from you.

Maybe he didn't get as many responses as he hoped, so he may have lost interest.

No matter what the situation is, if you think this is important to you, the best thing to do is to communicate with him directly and understand his real thoughts and feelings. Try to send him a message, asking him if there is any trouble or pressure, and whether your relationship has changed. Maybe he will be willing to share his thoughts and feelings, which will help you get to know each other better.