@MartyCormack I'm so sorry that happened to you. It's absolutely not your fault, but I understand why you feel guilty.
I personally would not have gone back because from what it sounds like, the owner never fully regained control of the dog. If you rode back there is the possibility it would have become hostile again, and out of control of the owner. This is why we have leash laws, and all pets are required to be on-leash in public areas...