Refetching an installed package, lost from /var/cache/apt/archives/?

[Erik Christiansen]

My /var/cache/apt/archives/ leaks, and after some time is empty.
I need a copy of the xpdf-reader package, to bucket-brigade to a
non-networked host, but on the networked host:

xpdf-reader is already the newest version.

Is there a way to force a fetch from a repository? Even:

# apt-get remove xpdf-reader      # Appears not to do any good:

# dpkg -s xpdf-reader
Package: xpdf-reader
Status: install ok installed      # It's still there!

And no, this doesn't help at all:
# apt-get --download-only install xpdf-reader

Nor does :
#apt-get --reinstall install xpdf-reader

put anything into /var/cache/apt/archives/ :-(

Erik