I've had that happen to me also. I bet it's happened (and is happening) more then I even know also.

One time I joined this yahoo group, and the club photo was a drawing of a chihuahua......not ANY drawing, MY drawing. I'm not stupid, I KNOW it was mine. You could tell they had cropped off my signature.

I *nicely* talked to the group owner, I just said, "Hey, I don't mind if you use my photo, but I'd like to have credit for it, and not have my signature cropped off." She gets all mad and is saying "My friend drew that, it's my dog, I watched her draw it!!" Um...NO.