My hens frequently pick out blanks. If they are not enclosed, they will sometimes carry them far away from the nest. I have found marked eggs carried 100 feet from the nest area, saw the hen walk past the window when she did it. Other times, if I have them enclosed, they will eat them. I think it is instinctive to not have something potentially rotting and giving off smells that might draw in predators.
Last year, I had a broody with chicks in a pen that a skunk dug into. I heard the dog barking and went out and smelled skunk. That little hen had whooped that skunk, had him cowering in the corner. Of course, not all hens will do this, but some are quite capable of some degree of defense.
My guess is that your hen did it.