I understand. This is part of life as a guinea owner. I very rarely needed to advertise keets for sale because people were constantly replacing the ones they lost.
I made sure that my guineas were shut in the coop at night and never lost any to predators. I did lose one to refusing to come...
Owls and other nighttime predators will also work over the guineas. A cat is certainly possible. I would expect coyotes to be present in your area also.
The reason for location is whether or not the missing guinea might be on a hidden nest. That is an outside possibility in you location but...
What general location are you at? A missing guinea here would be a loss to a predator or one thst took to the trees and refuses to land on the snow.
Guineas are a favorite for predators.