Like the commentators after this Drabbleclassics episode, the digging coming from underneath was the high point for me. It is the stand out moment of this story, the part I always think about when I look back on it, and it's so strong I actually wonder whether or not ending the story there would have been best. I mean, you have a twist that's good enough to end on, and you leave the reader to imagine just what the hell could be digging from the opposite direction.
But the part after the digging seems just as strong as the rest of the story, so who's to say it isn't better the way it is? Regardless, it's a great story, as presented.