Deleted messages
a certain contact of text messages got deleted trying to retrieve
iPhone X, iOS 15
Question marked as
If you are not using iCloud Messaging (Settings > your name > iCloud > Messages = Off) and they are all in your backup you can restore your iPhone from your backup. You will lose any data added since the date/time of the last backup.
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support