I just had a message this afternoon from Gretchen Farnsworth. Here's what she wrote:
 

Sadly there was a fight out by the island, I’m not sure if it was another loon or another species but the baby is gone. It looks like the original pair are ok and together, but I couldn’t see the baby when I went over that way in my kayak. So sad.

 Gretchen didn't mention whether she could tell if there's another egg in the nest that might still hatch. She thought a day or so ago that might be the case, and if so, there sill might be a chance this loon pair will have another chick. However there are no guarantees 
the same predator won't remember and be watching.