Unsolved Puppy Mystery

We've been trying to rejuvenate the lawn in the backyard so we set up some temporary fences around sections of our lawn. For the most part Pochacco and Mochi know not to cross the fences. But this is what we discovered one day after work.
1) Broken fences

2) Holes, patches of missing grass, paw prints

3) Mochi looking very innocent...muddy but innocent.