compacted store

I got fed up with the "we can compact your message store" pop-up and
foolishly gave my assent.
I very soon wished to look at a "sent" message and, of course, it had
disappeared. I am now going hairless trying to find how to recover my
"compacted" messages. Presumably nobody else has tried to do this, as there
seems to be absolutely nothing anywhere, suggesting that this might be a
desirable feature or even a possibility.
Just a simple message, about recovering this, to me, lost personal
information, would be nice.
—
I only came here because I was lost.