WhatsApp has unveiled a game changing feature "Delete for Everyone" on previous year (2017) for Android, IOS and Windows phone Operating Systems. This feature let you delete messages you've sent within 7 minutes for both sender and receiver. Nevertheless prone messeages cannot be accessible after the permanent delete, that denotes demerit of this feature. Unfortunately, "Delete for Everyone" option can be breakable easily. Any guess? A Spanish blog "androidjefe" have discovered new technique to read the deleted message. Changing date to old days to noodle the WhatsApp.
Alternatively using third-party called "Notification History Log" not only this application you can try other notifications monitor application like this. Pure Android OS doesn't even need any third-party app, just with setting widget you can read the notifications log.
#1 Android settings widget
Go to the home screen of your phone, then navigate to widget section. In the widget list find and select the setting widget. Long press to add to home screen to utilize the settings widget.
Now open the widget, scroll to the "Notification log" and select to view all notifications including deleted WhatsApp messages. This feature only available in pure android OS if you're using devices like Samsung then read the next option.
#2 Notifications Monitor
Install and launch the app "Notification History Log" ( For all notifications log ) on the app introduction screen it will ask you to enable permission otherwise it won't work.
It will monitor all the notifications based upon your need you can block list unnecessary apps. Notifications size limited to fewer size due free version. Keep in mind this app did not created to monitor WhatsApp messages. If you want to log only WhatsApp messages then you should install "WA Delete for Everyone | View Deleted Messages" app as usual enable access to notifications.