[Evolution] folder disappearance, filter 'on vacation'

["Daniel L. Johnson" <johnson danl mayo edu>]

Dear Experts,

Folders sometimes disappear from my sidebar, and filters fail to
function or disappear sporadically.

I'm using Evolution 2.22.3.1 / Foresight Linux / Gnome 2.22.3 and the
folder-disappearance event has occurred before.

Awhile ago, all the messages in the "Unread" search folder simply
vanished when I deleted one; there have been no messages in it for
several weeks until one unread message showed up 9/24 which has
persisted.

I was away from work yesterday, so the machine was unattended for 24
hours; evo is always open. When I came to work this morning, a folder
dedicated to a discussion group had vanished and the new messages from
the group are in my Inbox. (I haven't looked around to see where the old
messages are being displayed.)

This raises 2 concerns:
 1: it's a bug
 2: How do I recover the folder and its contents? I have about 10 years
of correspondence in it...

Thanks very much