Actually I didn't see any restrooms. Maybe it's hiding.
Funny to say, considering "park" is in the name, Heritage Park isn't really an actual park. :/ It's like a backyard to the Grove Middle School. The only restroom we're aware of is the one that's on the outside that's connected to the back of the middle school. I believe it's not a public restroom. There should be one though if Heritage Park is a "public park" ¯\_(ツ)_/¯
Thanks! Your answer is awaiting moderation.