You know, this is something that really nags at me about these murders. Assuming RA is BG and the abductor/murderer, he committed the crimes fully knowing that those three juvenile girls had seen his face, and would be able to place him on the trail heading toward the direction of the bridge shortly before the crimes. Whether the murders were planned or opportunistic, the girls described him as on a mission, and clearly the fact that someone had seen him was not a deterrent. It's crazy to me.
In regards to the phone issue, he offered the phone details up to the CO, so I think there was a reason for that. A hopeful alibi, perhaps. If the crimes were planned, maybe he really did look at a stock ticker, but then at some point turned the phone off, or hid it somewhere (maybe around the bench he later claims to have been sitting on), thinking if LE ever looked at his phone data, they'd see he was elsewhere on the trail. He didn't necessarily know how precise cell tower pings were. Although, this is probably unlikely because he would have later had to retrieve the phone, so who knows. JMO. Maybe knowing the three girls had seen him prompted him to do this with his phone. IDK...
If he only had a burner phone, though, I don't think he would have told the CO he was using a phone at all. Especially if he knew LE might get his phone data. Phone records would contradict his story, in that case. However, if he did have a burner phone (maybe besides his regular phone) then my question would be why even have a burner phone? I would be concerned that it might suggest he was contacting other people, monitoring SM or otherwise communicating with the girls, and/or using a recording function. What other purpose would there be to have one along that day?