If you post a picture anywhere online there's the chance someone will grab it for many reasons ... even with copyright.
Unless you have the $ and time to pursue the copyright violation ... the effort is often lost.
My son has been asked by magazine publishers to sell the copyrights to some of the automotive pictures on his website... which he has done.
But he has seen some of his pictures appear in unlikely places without permission.
A friendly legal reminder often results in the picture being removed.
At least the guy said it wasn't a picture of the car offered for sale??