Remember, as much as we love them, they are still animals and trouble may follow if we try to project our human behaviour on them. I always think of my pups as 2 y/o children and whatever I would do to keep a 2 y/o child safe, I also do for my pups. I'm referring to safety only here, not human behaviour (hope this isn't confusing!)
Remember we are the human and they are the dog. This was not his fault. Also remember, dogs live in the moment so he is long past that moment...you are the one who is dwelling on it. I also suggest reading or rereading info on NILF. Do a search because there's lots of good info on here (see Giselle's posts).
Good luck...he's still a greyt dog. Think of this as an opportunity to become a really greyt greyhound owner and move forward armed with lots of good info. btw a good dog is a tired dog. don't forget the exercise.
Hope this helps!