Related to the point above, the title of this episode makes sense. The kelpies sit between the two sides of the Ducktales universe's Sliding Scale of Anthropomorphism. They are the missing link.
It's also a Double-Meaning Title. A links is an old, Scottish word for a golf course. So an ancient, hidden Scottish golf course would, in fact, be a missing links.
Despite Scrooge complaining about Dewey "randomly hitting the ball", there does seem to be a kind of method to his madness. It's not traditional good posture, smooth swing, etc, but he does consider his shots in each time. The "lining up" of hitting through the rocks properly, the precise wind up of his sideways shot. So he does have a sense of how to play, even if he's unpracticed.
We see the statues of other golfers who've stumbled into the Druid Golf Course, and the kelpies mention our protagonists being the least fun victims ever. So...how many people have inadvertently stumbled into the magic golf course and either been drowned by our kelpies or caught by the mists?
In addition when the mists start getting closer the Kelpies offer to drown the McDuck family to avoid them being turned to stone. One can imagine how tempting that would be to someone with less resolve than them.
After Dewey wins the game and saves everybody... actually, no. He didn't. All of the golfers before them didn't revert or get sent back with them. Judging from the fact that Glomgold came back with his bottom half still turned to stone when they got back, that means that being in the mist long enough renders the stone effect permanent, and all of those golfers before them are effectively dead. If Dewey had been any slower in landing the put, Glomgold likely would have suffered the same fate. Even though Glomgold is a Jerkass who cares only about himself, it's hard to think that he would have deserved to be offed in such a way.
The implication from the sound effect, after he asks (and pays) Louie for help, at the end of this episode is that Louie strikes the stone on his legs with a golf club so that the stone shatters. Meaning Glomgold like the other ducks was just covered in stone, but the stone had become more solidified and clingy. He's back to normal by next week's episode. The other victims are still screwed, though.
Earlier in the episode, after getting fed up with how boring the golf game had been up to that point (just before the kelpies come on the scene) Louie rants that he'll be walking home and starts making his way back alone... while the petrifying mists start closing in. If Louie hadn't been called back, no one would have noticed him turning to stone until it was too late to reverse the process.
