I agree with the others that putting a message or an icon on the main screen is probably just going to unhelpfully clutter the screen and not really do anything to mitigate the issue. If you forgot to check that you're on the main screen before dropping the skull, then how is putting a message on the main screen (that you forgot to check) going to help in any way?
The solution already exists, as it does for many things in life: just put your finger in the hole.
The solution already exists, as it does for many things in life: just put your finger in the hole.