I was there with a separate crew on Friday as well. Our group of 13 was ahead of the trip that had the fatality. We had just routed 25 miles of the impassible canyon at epic highwater, and were just getting our stoke on at the takeout, when a pickup truck comes barreling down the road and said that an unmanned raft was floating down toward us from the confluence. Our crew threw a couple of kayaks in the truck, headed upstream and somehow managed to tow the boat (right side up but no oars) into an eddy below Cranmer Creek (props to Kate Wagner for that!). Our crew then floated it down to the takeout with loaner oars, thinking someone would soon be by for it.
An hour later, a different truck comes down to pick up the raft, and the driver (who was part of the group with the fatality) informs us that the oarsman had died. I didn't get the full details on the accident, and didn't want to pry. The driver was thinking that a heart attack may be been involved, but it seemed speculative. I'm sure others know a lot more than I do about the accident.
My deepest condolences to everyone on that trip. It was really awful.
Never heard or saw the two other missing boats. Maybe they were ahead of our group to start with? We probably got to the ramp about 5ish and maybe left about 7:00 - 7:30 pm.