Let's play "hide the marble..."

I usually notice whenever any of the dogs seem to have something 'special' in their mouths (you just wouldn't believe some of the things I find when I'm doing my poop patrol...) which I then have to check out, and more often than not take whatever it is away from them. In this case, besides me, Elizabeth has also noticed that Minnie seems to have something she doesn't want anyone else to know about, an attempt to hide it which seldom works. He expression is a dead giveaway...