I think that the vanishers stay out of sight and out of touch for several reasons:
1) The old team (i.e. your family) knows everything about you and may see through some of your truly stupid plans and ideas so, to put that criticism to bed quickly, just cut them out of your life.
2) They lack impulse control for their addictions. Removing the spouse is really just clearing the field of an obstacle to their fantasy life. It is pesky to have old remnants hanging around cluttering your vision of the "New Perfect Existance". Childlike, I know, but they really want to maintain the fairytale as long as possible.
3) The MLC behavior is abominable and I believe that even the MLCer knows that. He/She knows that the things they have done are shameful, and shame is a driving motivation for the MLCer to run away. After all, what child wants to face up to the appropriate punishment for their actions? Well, put MLCers in that category too.
4) Vanishers may, more than some of the other types of MLCers like Clinging Boomerangs and Low Energy MLCers, have viewed the spouse as more of the parent in the relationship (mine did, I was like his Big Mama, cleaning up his dumb messes, paying his bills, running his errands, etc.) When they enter MLC, they want to be grow up (or we think that they aspire to that developmental goal, or at the very least, they aspire to "freedom" without a parent-figure in the picture) so they gotta leave Big Mama's nest, and like a teenager, they do it with a flare for the theatrical.
Reading through some of my spouse's diary that my son had given me (thus peeking into the head of an MLCer), he was trying very hard to recapture his integrity. Apparently this plagued him deeply (yes, guilt and shame are motivators). He wrote crap like, "I am a man of my word," and "I am faithful to my Significant Other", so that I almost died of laughter (it was more the irony, than outright funny) when I read these things. Who is he kidding? He still envisioned himself as a man of integrity and his word, even after walking out on his family without so much as 5 min notice after 26 years! He's faithful to his cheating and lying co-worker? [What a Thought! And both lack any shred of integrity]. I have trouble picturing how anyone could begin to think that they have integrity when one has so callously disregarded his family in this manner. He also lamented about "I don't belong anywhere". Pathetically all of these are consequences of his own selfish actions that lacked any moral fiber at all. It is all so ridiculous. Guess in his case, you don't realize what you've lost until you can't regain it. Honor and dignity are tough items to reclaim. So I think all those things about shameful behavior are why the Vanishers stay vanished and out of sight.