This trick revolves around the notification manager feature of the Android OS. This is a system feature of Android which keeps track of all the notifications which you receive on your phone. It keeps a snap of all the notifications on your phone so if you can access it, you can read all the notifications there. If that message has been received on your phone then you can read the message which you received on your phone.
Steps to Read Deleted WhatsApp Messages
Download the app called Notification History from the Google Play Store. It is the app recommended by the blog who found this trick for the first time.One the app is downloaded, you have to search for the deleted WhatsApp message in the notification history. If you are using the Nova Launcher then it will be easier to do that.To access the notification log, tap and hold the home screen select Widgets > Activities > Settings > Notification Log. This will put a shortcut on your home screen which lets you access the notification log. This can be done on stock Android launched, just select the Settings widget in the widgets picker.
Wrapping up
The trick only works for Android smartphones, there are no tricks for the WhatsApp on iOS. We will keep you updated if there will be any trick for the iOS user as well.