I recently booked a ticket on Delta for a 15+ hour flight through a travel website. Due to dietary restrictions I specifically chose my meal preference in that ticket. This never got updated with Delta, but was visible in the travel website's site. This resulted in no meals of my preference being available on board- which means I had to go hungry for those 15 hours. I contacted the travel website and they said they would research and get back to me, which they haven't. I haven't contacted Delta because it doesn't seem their problem.
What steps can I take so I am compensated for this (if at all I can) ?