It's the curse of Google images. If it comes up in search, it's on the internees so it must be free to use. Or that seems to be the mouse operandi.
It can be immensely frustrating, some will be willing to give uou a credit once you contact them, quite a few just ignore you.

I have a wardrobe full of the t-shirts. I rarely put any photos on the Web without a watermark anymore and only leave them up briefly.