My dog was attacked at a dog park for ignoring the dog?

Last week I took my girl to the dog park for some exercise and all was going well until another dog came in. He was plainly dominant (by his posturing and behavior) and all of the other dogs submitted to him but my dog ignored him and ran around with her toy in her mouth, playing with me. She tried to avoid him when he tried to control her...but he eventually attacked her. Both dogs were fine but I'm wondering if he attacked her because she wasn't paying attention to his dominance or just because she's so full of energy/anxiety that he was trying to correct/control her. If it helps any, it was an non-neutered young Rottweiler male, and my dog is a 2 yr old spayed German Shepherd. She never tried to fight back until he suddenly knocked her over and started to fight with her. I'm thinking he was simply out of control, but I want to make sure my dog wasn't in the wrong either since he only attacked her (again, she was the only dog to pay no attention to his antics, but she also seems to be the most unstable dog there sometimes--she's not aggressive or anything, just anxious and hyper). Please, no mean replies, I really would like to know for sure. It's not the first time she has been attacked. I'm not mad at the owner or anything- scuffles are to be expected at dog parks.