I seem to have experienced the same thing, because there isn't a glummycube in the SaltyDKDan area. What I ended up doing to get there was jumping on another glummycube, and twiddling my thumbs (in my case, doing schoolwork while looking back at the screen every so often) for an hour while I waited for it to randomly slide until it finally got to the platform leading to salty. Mind-numbing, would not recommend.
Hi! For anyone else dealing with this problem, this is intended behavior of Lost Dog. There's actually another route! Starting from Lost Dog, go around the edge (shaped like an up arrow) and turn left; There's two gaps about the width of a Glummycube that you can jump; one forward and one for the right.
To jump these gaps, sprint until your camera just *starts* to dip down, then jump. Go around and you'll find your dannyboy!
Unfortunately, I did all this assuming he was the last one to find, and it was the sheep I was missing this whole time lmao