Trailhead Parking can be found in the day use area at: N45 29.816 W121 49.242
UPDATE: This spring, they brought back all of the old campsites in this area. In order to get to this, you will have to bushwhack around, or go through, the most North East of the restored walk in campsites behind the day use bathrooms. I could not find a good trail around the campsites to get down to the waterfall. All the old orange and pink trail markers are now gone, because they have put a gravel trail through the old campsites. Please, if someone is camping in that campsite, respect their privacy!
Welcome to Lost Lake! This location is one of the oldest developed parts of the campground. In fact, 15 to 20 years ago, they decided to make many changes to the campground. and this area was returned to nature and closed off from camping. They then developed other areas that are a little farther from the water for camping use. The trail starts just behind the toilet in the day use area, and you’ll be traveling a very little used (or known) trail to a beautiful waterfall.
You’ll be traveling through a few old campgrounds, so you’ll see some logs fallen across old picnic tables, as well as a couple old fire pits. As I said, this area was returned to nature, this really is the trail. You’re on the right track, so follow the sound of the water, and you’ll find it. It’s a little rough in the first 100 yards; the trail will be more clear from that point on.
The cache itself is about 20 feet from the trail, away from the creek.
There’s another less spectacular waterfall about 200 yards downstream.
For a truly excellent 3.5 mile, 3 cache hike, I’d park in the day use area, walk south to the old growth trail and do the old growth trail cache, continue on and do the huckleberry mountain cache, then continue clockwise around the backside (west) of the lake to the day use area where you’ll have spectacular views of Mt. Hood (bring your camera!), and finish up in the day use area with the hidden waterfall cache.