I hope I'm not ridiculed when I do this but I'm going to say goodbye if I decide to leave. I'll say something like:
"Thank you for all your love and support. You've gotten me through a difficult time and I really appreciate it. If I come back soon, it's just that I missed all of you. If you'd like to reach me, I'll still be using my facebook account. My name is Paul Suf. Please friend me."
Just like when Mouthy was gone for awhile. She let us know the situation so I wasn't worried that she died or something.