As the phone was found under the bridge, I would suggest walking the rail line from the bridge to Colombia. Rail right-of-way is an easy egress route that avoids public attention. At Colombia, it turns at the river and goes North, under 30 and past Chickies Rock County Park and the popular rock climbing spot. I would have LE and Park Staff check with regular climbers and see if anyone saw him, if so that would mean he was following the rail right-of-way North. If not, the next logical guess is the Susquehanna River. The river search area would be from Colombia South to the Conowingo Dam at RT 1. A print evidence search along the river at Colombia "could" help establish in the water or not.
Dogs may have difficulty with tracking on the rail ballast (rock) since the snow and rain, and the uneven footing would be difficult for the dogs and handlers (speaking from experience).
