As someone pointed out earlier on this forum, the killer would have to be a complete idiot to return the body to that park a week later. Im sure there are infinitely more sites that would be less risky than returning to the very park that has been the focal point of the investigation.
Besides, in the PC, the officer said they believe Blaze had been there since the night of his disappearance.
Correct as a local, I can tell you not far from this park is miles and miles of back county with hiking trails all over the place. You could hide something here and it would take forever to find. So leaving it in the park I think was knee-jerk.
https://goo.gl/44wiQo
is a map of the area, if you zoom out just a tiny bit you can see what I am talking about.