Unfortunately for you Tim, you and your dog have been reported to the authorities. So he's in the system now. If something happens again and you're reported, your dog may have problems with the county or state in the future. (You've been warned.) In some places, worst case scenario...your dog will be put down. I would never have given my information to the other party if my dog didn't cause injury.
On another note, we've all talked about this ad nauseum...the dog park debate. This is exactly why I don't take my dog to the dog parks anymore. Incidents like these are bound to happen. And you may view it as harmless dog behavior, but there are always (uneducated/uninformed/unknowledgeable) people out there who don't see it that way. There are also people out there with GSD prejudices. It doesn't matter if your dog started the fight or not, because of the breed you will always get the blame, unless there are fair minded witnesses.
Also, I've never had a female dog so I don't know anything about heat cycles. But isn't that when they're "hormonal?" Is that the right time to bring her to the dog park? Not criticizing...just a legit question/concern. If it's not a an actual thing, then just ignore this last paragraph.