There were actually 14 "keep" votes. This should mean that it couldn't have been automatically reaped. I asked a few gods if they had reaped the node by hand and was not surprised to hear only "no" responses. There still may be a member of gods that did the reaping that I didn't talk with. Or there might be a security problem that allowed a non-god to reap the node. Or there might be a bug that caused the auto-reaping to happen despite the "keep" votes.
But my best guess is that one of the gods reaped the node by accident. In any case, it will be unreaped soon (no, I won't go into the details of why I can't just unreap it now).
And I'll keep my eyes open for evidence of the other possible explanations.
(but my friends call me "Tye")