Insert heavy sigh here.
I don't have the time now to investigate the annoyance. But I do wish I understood how posting a comment, without touching the template in any way, shape, or form, causes the information to vanish in a puff of smoke.
I'm hoping it will reappear as quickly later today. Hope springs eternal.
Update: 11:13 am
It's back, or at least some of the sidebar is visible again.