Keep a bowl of feed along the run? fencing during the day (assuming the other two are in run during day). Since the turk was in the yard it is probably roosting pretty close at night (I'd take out a spot and check for eyes in the trees). If it is roosting nearby you might be able to get it down and back to the coop, 12wk old shouldn't be in the top of a 60ft. hickory. We would shoot a leader, tied to an arrow. over the branch ours had taken possession of, pull over nylon cord with a empty gallon jug tied to it and slide the sucker along the branch (knock the turks off and into the circle of `spotlight' on the ground - then carry them off). They got the idea pretty quick (only had to be `moved' a couple of times).
We kept ours in the run for 4 months, only letting them range an hour before sundown and only when we were around (still liked to fly up on chimney, but they could be hosed off, or bowled from branches with `bottles'). To herd them, hold 6-8ft. long sticks in hands out to the sides, otherwise moving them becomes a nontrivial task.
Good luck!