Here step by step the right procedure to hide the Phono notification from the lock screen.
Go in Setting and choose "Sound & notification"
Choose "When device is locked" option
Than "Hide sensitive notification content"
Go to Phono preferences and tap on "LockScreen Notification" and choos "NO"
NOTE with the "Hide sensitive notification content" option active ALL the notification will have the sensitive text (normally the sencond line of that) hidden.