I've been using the Scrapbook extension http://amb.vis.ne.jp/mozilla/scrapbook/ a lot for the last month to store parts or complete sites for off line reading.
Unfortunately i only spidered a few documentation pages (which have been restored already) of ubercart.
But maybe, just maybe some other ubercart/firefox lover still has an ancient scrapbook copy lying around. If you do, maybe you could email it to the ubercart people, i guess it could come in handy to restore their data.