How to recover if I accidentally lose the full screen text key on my mobile phone?

You can restore it in the settings.

Specific recovery methods: 1. Open the "Settings" application on your phone. 2. Select the "System" option from the drop-down menu of the settings interface. 3. Next, select the "Backup and Restore" option on the system interface. 4. Select the "Cloud Backup" option on the backup and recovery interface. 5. Next, select the backup date before the SMS icon disappears on the cloud backup interface. 6. Next, select the "Restore" option in the lower right corner of the backup details interface. 7. Next, select the "Restore" option in the pop-up box. 8. In this way, you can retrieve the disappeared text message icon.