If only, you ask the question we all wish we knew the answer to. I can only tell you my experience with my H. He was a boomerang then vanisher then clinging boomerang then vanisher then we had a reconnection then vanisher for the last year. If it weren't for my S, we would probably have no contact at all.
During his vanishing moments, if I didn't contact him, he would not contact me ever. When I do contact him, usually to ask him for some help for practical stuff, he then sends me back tons of emails. So my impression is that he doesn't contact me because he's scared of me. I think vanishers are ashamed. They know what they did was really bad, that they themselves would have judged someone who did what they did as bad. It's still just guilt, thinking of themselves and how they appear to others, maybe some shame when facing people they feel judged by, but that's easy to fix in their heads: just stay away from these people. So I guess the more shame they feel, the more they stay away.
A very good friend of mine from childhood is a doctor and her H went through a MLC. He was a wollower with no OW. She knew about MLC because she had studied it during her medical course, you see they do know about it, so she probably made fewer mistakes than we did. She had very strong boundaries and enforced them. They were boundaries about treatment of the kids and not selling the family home. She wasn't scared to tell him what she wanted. She was never rude though and never screamed.
She always stressed to me the importance of maintaining contact. She forced her H to phone on the house phone once a week to speak to their boys (he had up and left the country to work on another continent, didn't see the boys for 6 months), and every Saturday, she would answer the phone herself and just say hello how are you doing.
She says we must keep the communication line open if we want to get back together. She told me she had no expectations of him coming back, had no idea if he would, he was nasty monster, but he did go back, and they have been very happy since he woke up. His awakening was sudden, and once he came out of the fog, that's how he described it, he said he couldn't even remember why he'd wanted to leave in the first place. So you see, some do come back.
Since you seem to want to have some contact with your H, I would suggest as others have, a little email every couple of months. No pressure, no emotions, no relationship stuff even if he drags the conversation that way. It would be best if there were a real reason to communicate like if you needed some information from him, and then keep it brief.
You really can't make it worse. Do want you want to do, just don't judge them. They have a knack for triggering us and then we can get all accusatory on them, it doesn't work, actually that is when we do make things worse. Just don't be too sweet or too cold. Think of a work email. Polite. Good luck.