Taking ownership

I purchase two meals from Nando through Mr. D Foods. My lunch was delivered with the bag halfway sealed. By the time I realized the delivery guy was already gone, somebody might have eaten or even touched the food in the bag. I was just wondering who was responsible. It seems to me that the restaurant is responsible for sealing the bag. I lodge a complaint with Nando's and they did come back to me and they advise me to go via Mr. D Foods. Even though I thought Nando must take responsibility, I filed a complaint with Mr. D Foods. No other communication from M. D Foods or Nando's.