Why did the SMS disappear when the phone was backed up?

It depends on the time of your last backup. If the backup time is too early, the subsequent content will be lost.

The purpose of mobile phone backup is to back up the data in the mobile phone, including address book, SMS, call records, application software, games and other important data to prevent data loss.

Software backup is to upload the mobile phone data to the cloud for data backup through the installed mobile phone software, and then download the data to the cloud next time. Well-known mobile phone backup software includes Leshun mobile phone backup software developed by Lenovo Group (under the operator's banner), China Mobile Cai Yun Address Book, Tianyiyun, QQ Address Book, 360 Address Book, DBank Android Client, iUU (Love to Travel), Mobile Phone Brother, Push-to-Talk and so on.