Hey, I was there when you guys walked up.....when I loaded up my crap and drove back down, I saw the boat sitting at #6 next to the bleachers. I'll keep my eye out for the few hood rats that were walking around the park during that time-frame. I'm thinking non-boater theft....punks are the culprit.
I wouldn't be surprised if they just threw it in the water, if I were you, I'd consider talking a walk/drive down the river from that point. I can't imagine too much interest from the theives in actually using the boat.
I'll take a look around for ya.