deleted IMP messages

[Dana]

I had a page of messages I was saving disappear the other day.  It's
possible I inadvertently deleted the messages, but I think not.  The two
step IMP delete process is a good one and goes a long way toward inadvertent
deletion.

Does IMP move saved messages to an archive, file automatically, or auto
delete either after a certain quantity is reached, or a certain time has
expired?  If so, how do I access/retrieve them?

I know that if I inadvertently deleted them, they are gone.

Just curious.