Check the Messages app and search for the conversation or keywords
Check Recently Deleted in Messages if your iPhone is on iOS 16 or later
Restore from an iCloud backup made before the messages were deleted
Restore from a computer backup made in Finder or iTunes before the messages were deleted
Turn on Messages in iCloud if it was previously enabled and sync again
Ask the other person to resend the messages or screenshots
Contact your carrier to ask whether message records are available
Use a third-party iPhone data recovery tool if no backup exists
Stop using the iPhone if you want to maximize the chance of recovering deleted data
Back up your iPhone before attempting any restore process