Getting There: Take Hwy 569 at State Hwy 1 near Anaconda that connects with Hwy 43 between Wise River and Wisdom; the turn is near the "Stack". Turn right on Hwy 43 towards Wisdom. Stay on Hwy 43 for 7 miles, passing by the Fishtrap Campground, then a right on Calvery Creek Road for about 5.25 miles and then right on FS road 1229 for about 4 miles. 
You will pass the trailhead for the West Fork Fishtrap Creek at the 2.5 mile mark just after crossing a bridge, it has a nice informational sign.
At the Middle Fork trailhead there is a parking area on the right with some signage (No Motorized Use) on the left where the Middle Fork trail takes off, no trail sign or numbers. While researching this route, I found a couple other posts about the route: Eric Higginbotham's Description and Aaron Schye's Description. Both descriptions are informative. If you go up the road for less than a half mile there is a nice spot to camp on the left.
The first 1.25 miles is flat until you cross the meadow. Don't overthink this, just head straight across in the same direction as the trail and the trail picks up on the far side. There may be a visible path across the meadow depending on the amount of traffic on the trail. The trail then climbs steeply to the Wilderness Boundary.
You get a quick break and then it is uphill (not as steep) for a while. The trail then heads downhill for a short distance then levels off or climbs easily for a while giving your calves and lungs a break. Soon, you will come your first creek crossing of the day, which is a bit more than halfway to the saddle where trails #129 & #128 meet. You can hear the water running above you before you get to the crossing.
Take a look at how the creek is formed and running. My son, Colter believes that this is a manmade feature to divert water from the Middle Fork to Swamp Creek. The stream runs nicely along the contour before dropping into Swamp Creek and appears to be dug out. From this crossing the trail climbs again before hitting a flat and a series of swampy areas and small stream crossings. The trail tends to wind all over the place in this section.
Eventually, the trail will just end at the marshy area that seems to causes issues for some. Again, don't over think this, head straight across the meadow in the same direction the trail enters the meadow. You will have to adjust a bit to avoid the wetter areas, but on the other side there is a blaze and a large cut log where the trail picks up again at the treeline. There is no need to swing left into the trees and do not head deeper to the right/uphill into the meadow.
The trail then starts to climb steeply for the remainng distance to the saddle between the Middle and East Forks of Fishtrap Creek. This is a rough and rocky section and is not easy either going up or down. There are a couple places where some deadfall interfers with the navigation, so don't be in a big hurry. As described by others there is a sign and fire ring on the saddle, which is the 5 mile mark and over 2,200 elevation gain from the trailhead. There is a trail (covered with deadfall) that takes off to the left up the ridge toward the peaks. The unmarked trail is in good condition and easy to follow as it stays just below and right of the ridge crest.
Eventually, the ridge will become much steeper, cross East Fork of Fishtrap Creek at that point then work your way up a more gradual slope to a flat just below the Lost Lakes. There is a nice campsite at 9,200 feet with a fire ring and the creek is just down the hill to the left a short distance. From the campsite you can see the notch for the outlet of the Lower Lost Lake, it is a steep climb straight up the talus slope.
The Upper Lost Lake is nestled up against the lower cliffs of East Goat Peak. West Goat Peak sits to the right from the lakes with both ridgeline routes clearly visible. Unfortunately, the time we did this hike it took us almost 4.5 hours to get to the lakes; estimated at 6.5 miles with 3,150 feet of elevation gain; and I was running a bit low on energy.
So we decided not to try for the summit. We went to the upper lake and had lunch, looked over into the upper LaMarche Creek Drainage and at Cutaway Pass in the distance, then headed back down, arriving back at the truck in 3.5 hours. My old knees were definitely protesting on some of the steeper parts of the trail on the way down.
If I were to attempt this again (2025 goal), I would backpack into the upper camp below the lakes, get up early and climb West Goat to beat any thunder storms then break camp and hike out in the afternoon. The hike in would be hard with a light but full pack, but I now know the trail and creek crossing so I know what to expect. We found the trail easy to follow and never had any issues losing it. Stay patient around the deadfall and marshy areas, there are many blazes and cut downfall on the trail. The trail is steep and rocky, but there are nice flat sections that allow good recovery strolls.
I will update this entry for the full summit entry in 2025 when I get to the top. Colter and I did make an attempt from the Warren Lake side way back in 2010 on his 50-Miler Merit Badge trip with the scouts, but got run off the mountain at the 10,000 foot point by lightning that afternoon.
