Footer image issue

I am trying to work on a site that someone else has coded and sent to a devtest. They are asking me to replace an image on the footer and I’m not sure where to locate this in order to replace it. I have looked through the source code on the website and looked into the footer.php file and gone through the media and don’t even see the original image that they have on there. I understand this is a basic question and probably has a basic answer, but any help would be great thanks.