I thought sister Tammy said the bikes were found leaning up against a fence when LE arrived. (A reporter on live chat said the bikes were found by fire personnel.) If they were on the path and found against the fence, someone moved them.
Yes... I think the question is WHO moved them, and when? The why is pretty obvious, it sounds like they were a hazard for other bikers. I can imagine the guy that nearly crashed into them initially thinking "damn kids leaving their bikes all over the place" and then hearing later the girls were missing. If it were me I wouldn't think twice about moving the bikes off the trail. But I don't recall him saying he moved them.