I have not been on the Lost Creek trail beyond Grinnel Ridge (from South Fork). But between the ridge and South Fork trail, it is unnavigable. But it’s not very far to just drop straight down to the South Fork and pick up the trail.
I am wondering about your route choice though. Any particular reason why Lost Creek rather than just taking the South Fork Trail to the Dollar Lake/Saddle trail?
On the fishing front, there will be nothing on the way in. Nothing that I’m aware of anyway.