This doesn't happen often, but I'm almost certain this has happened more than once so I should say it: If someone disappears from BLF without a trace, don't put them in the spotlight by starting a thread asking about what happened. They probably disappeared for a reason, and doing this just makes it worse. If you want to ask questions, contact them directly. Just don't make it public.
Also, if one of these threads does get made, don't speak for the person in-question. Odds are you're spreading misinformation and asking more questions than you are answering. Instead, let them know the thread was made so they can go and answer it if they want to.