Why do some mobile phone text messages disappear completely after only reading them once?

It was your classmate who installed the function of Zishan Telecom. If your system is S40 or S60, you can also install it. What you can't get from the text messages you have read should be the unique function of the message, or you can set the message hands-free. In other words, you send a message to a friend, and your friend takes out his mobile phone and displays it directly without opening the message. Press enter after reading it, and it's gone. The software is free.