You are not in any trouble if the officer never contacted you and got your information. If it was 9:30 then you weren't out past curfew.
"Nothing in this communication is meant to establish an attorney-client relationship. The information is provided for educational purposes only. No action will be taken on your behalf unless you have have hired me and entered into a written retainer agreement. I am only licensed in Tennessee and I suggest contacting an attorney in your specific city and state as soon as possible to avoid any statute of limitations deadlines, if applicable."
No worries now. In the future keep in mind most parks usually have a sign posted which designates the opening and closing hours of the park. Remaining on the property after hours can result in a criminal trespass charge if you're not careful.