Hey there Longnight7,
It sounds like you need some help locating and managning message attachments.
Following How to check the storage on your iPhone and iPad will help ensure you're looking in the right place.
Tapping Settings > General > iPhone Storage > Messages should present you with a list of document types Messages is storing on your iPhone. Tapping one of these categories should provide additional details and specific files.
You can also locate attachments following Use Messages on your iPhone or iPad
"Find attachments from a conversation
- Open the message.
- Tap the name of the contact at the top of the message. If you're using iOS 14 or earlier, or iPadOS, tap the Info button .
- You'll see Photos, Links, Documents, and more. Touch and hold an image or attachment to show options like Save, Copy, Share, and Delete.
From your conversations page in iOS 16.2 and later, you can also search to find photos in Messages based on their content, like a dog, car, person, or text."
You may also be interested in seting up iCloud for Messages.
Set up iCloud for Messages on all your devices
Have a good one!