I see that text message notifications won't stay put on the lock screen. You've even seen, at times, where it simply disappears. I'm happy to help.
Use notifications on your iPhone, iPad, and iPod touch -- Tap Settings > Notifications > Messages, then change the banner type from "Temporary" to "Persistent".
Change alert styles and settings for notifications
Customize your notifications with different alert styles so you can quickly act on emails, calendar invites, messages, and more.
To add or change an alert style for a notification, go to Settings > Notifications and select an app. Here are some alert styles that you can choose:
- Allow Notifications: Turn on to get notifications from the app you selected.
- Sounds: Have an app play a sound to alert you when you receive a notification.
- Show on Lock Screen: Turn on to see notifications from the app on your Lock screen.
- Show in History: See previous notifications from the app you select.
- Banners: Choose how you want notifications to appear when your device is unlocked. Tap Temporary to have alerts appear on the screen and then go away. Or tap Persistent to have alerts stay on the screen until you act on it.
- Show Previews: Choose what you want to see when you get a notification, like a text message.