Help: iMessage Reaction Notifications for deleted texts
I’ve seen this question pop up before and I have not found a clear answer.
To resolve this, make sure your iMessage notifications are enabled for your Lock Screen.
Go to your Lock Screen, swipe up to see your Lock Screen notifications, you should see the reaction to your deleted message, tap on it (don’t swipe it to clear it). This should open your phone to iMessage and restore the message. From here, you can back arrow to your main iMessage screen and see the message with the notification, open it again, and the notification will disappear.
iPhone 12 Pro Max, iOS 15