Thanks for sharing, seeing the pictures takes away some of the disappointment. I think the location of the yarder must be the far southeast corner of the lake. I followed the creek down which should've put me right on top of it according to previous accounts. I think the creek's output has shifted a couple hundred feet to the west over the years.
Other's caution is well founded, in addition, I'd recommend bringing a decent snack with some carbohydrates to consume at the bottom. I hit the wall (ran out of carbs) on the way up and wasn't able to sustain the exertion required to scramble up some of the very steep slopes (had to stop often bracing against trees to prevent sliding backwards). I'm 40 years old and not in excellent shape but I did hike 12 miles with 2700 feet of elevation gain the weekend before.
The steepness and having to climb it at the end is the biggest danger in my opinion.
Also, I believe it's technically against the rules to travel off trail anywhere in the Mt. St. Helens National Monument/Forest
