I had difficulty finding the specific trail on AllTrails, but now I've come across a sub-segment of the trail posted there. Interestingly, there is a caution that it can be difficult to find the trail as you come out of the village.
I presume they are referring to finding access to the bridge since they reference signboards and roads (and there are no roads across the bridge). I also noticed that immediately after crossing the bridge there is another trail that splits from the Kohechi. It isn't a very long trail (perhaps several km), but perhaps it has some difficult terrain?
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https://www.alltrails.com/explore/t...bridge?mobileMap=false&ref=sidebar-static-map
On Help Find Pattie on FB it is mentioned that this trail has been searched extensively