Newsletter envelope "icon" not a graphic

[digitalt]

I'm putting the finishing touches on my site and ran into a graphic that doesn't appear to be a graphic. I used Firefox to inspect the element for the newsletter sign up image and it doesn't show as a graphic. I looked in all the image folders and not there either.  I need to change the envelope picture but this one I can't figure out how since there is no graphic to change. Am I looking in the wrong place?

[Basara]

Please post screenshot

[digitalt]

Attached is a screenshot. I want to change the envelope.

[Basara]

Hello. This is FontAwesome icon see how to use it in CSS http://stackoverflow.com/questions/14736496/use-font-awesome-icons-in-css