I don't think anybody mentioned enema or colonic, but with some blockage like this local to the anal area, that might be a good option. In any case, it's really not optional to skip it the morning after, or even a day after, so I'm not sure why the poster didn't mention it.
There is no substitute for good preparation, eh? The malic acid has to be the key, plus the epsoms in timely manner. Just don't skimp or skip. I have been adding malic acid (powder derived from apples) to the apple juice, not wanting to err on the side of not enough.
What's amazing is that this stone somehow passed through to the colon without any apparent problem. I wonder how that is possible?