Deleted messages

Deleted iMessages are saved on your latest iPhone backup to either iCloud or iTunes. Restore a backup that was made when the messages were present, and they (and most everything else about the iPhone) will be restored to the state it was in when the backup was created.

https://support.apple.com/en-us/HT204184

If you were syncing Messages using iCloud, you can't recover it.

How do I recover my deleted thread from messenger on iPhone