How photos are used

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I uploaded a few photos several months back. Now, one of my pictures always shows up as the icon for CATS. But when I look in the "My Photos" section on my profile that particular picture doesn't show up. Why isn't is also showing up in my photos in my profile? How can I know if I got credit for it being used in an interest? The fact that it is not in My Photos makes me feel like it was taken from me. Also, can anyone tell me how to upload a photo to go along with a response?