There is a square chat balloon icon or chat bubble appearing on the notification panel on the top left of screen. What does that indicate ? It has a call out arrow on the bottom left.
Taking into account that it is a chat bubble icon, it means that you have got a new message from a person while the chat/message app was closed or in the background. I think that it is almost the same as the chat notification indicator of 'Facebook lite' app
Through help in another forum I was able to find out what the square chat bubble icon with the left callout was on my phone... an indicator that my Walgreens app was running in the background. I was able to set up a widget on my screen (hold, select widgets, select Settings 1x1 and drag to screen, select Notification Log as type) which shows my notification log and Walgreens has been running and/or using battery all-day every day for a few months. This is a problem as I do not often actively use that app. Guess I'll be uninstalling Walgreens.