Disappearing Text Messages

Hello there SandPhx,

Welcome to Apple Support Communities. This could be caused by low internal device storage. So, we suggest checking the storage on your iPhone following the steps in the Apple Support article: How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

"Use your device to check its storage

Go to Settings > General > [Device] Storage. You might see a list of recommendations for optimizing your device's storage, followed by a list of installed apps and the amount of storage each one uses. Tap an app's name for more information about its storage. Cached data and temporary data might not be counted as usage.

In the detailed view you can:

• Offload the app, which frees up storage used by the app, but keeps its documents and data.
• Delete the app, which removes the app and its related data.
• Depending on the app, you might be able to delete some of its documents and data.

Use the Finder or iTunes to check the storage on your iOS device

1. On a Mac with macOS Catalina 10.15 or later, open the Finder. On a Mac with macOS Mojave 10.14 or earlier, or on a PC, open iTunes.
2. Connect your device to your computer.
3. Select your device in the Finder or in iTunes. You'll see a bar that shows how much storage your content uses, divided by content type. 
4. Move your mouse over the bar to see how much storage each content type is using."

Let us know if this helps you.

Cheers!