A drowning person will reach out and grab onto anything. They'll let go of it as soon as they feel safe again. How many of us have done the same thing at other places. Our bi-weekly swearing off drinking and our anual visit to an A.A. meeting are the same thing. We've all done it. We've all said "This is it. I'm done", only to return to drinking before the weeks end.
Don't take it personal, it just wasn't their time to quit.
It's possible they found another site or another way to stay sober and decided to never visit SR again for some reason. But I doubt it.