What is this mysterious letter S icon?

[PacificaBren]

A friend of mine is trying to figure out what app or service is causing this letter "S" to appear on her phone's lock screen.

Does anybody recognize this icon, and can you tell us where it's from?

I'm talking about the letter S that is between the planet icon and the +3.


Thank you!

 

[Rob]

I think there is a good chance it's the Shopkick app:
https://play.google.com/store/apps/details?id=com.shopkick.app

You can find the Shopkik Forum here for further discussion:
https://androidforums.com/apps/shopkick.726/

 

[PacificaBren]

Thank you Rob, your input is greatly appreciated. Somebody suggested in might be for Shutterfly. The font for this "S" looks closer to the Shutterfly logo, but it also looks a lot like the font that particular phone is using to display "Sun" as the day.