[Evolution] suddenly empty sent folder

[Carpet Nailz <carpetnailz researchintegration org>]

Any idea what might cause my "Sent" folder to be suddenly empty? All the
other folder are OK. Last time I looked there were probably over 1000
emails in the folder, so I can't have selected all of them and deleted
them--at any rate they would then be in the "Trash" folder, which hasn't
been emptied for several days.

I've tried restarting Evolution, but that didn't help.

Thanks.