Sync overwrote existing bookmarks instead of "syncing"... how do i recover lost bookmarks?

Decided to try and use the bookmark option in FF 4 Sync. I had been using the other sync options without issue. My goal was to get my work PC's bookmarks synced with my home PC. I turned bookmark sync on my work PC, when I got home and booted up my computer, before I realized what had happened FF had overwrote my bookmarks on my home PC with my work PC's bookmarks. I have now lost ALL of my bookmarks on my home PC. How do I recover these?

I didn't have time to try and save my bookmarks from my home PC, apparently when you set the one instance of sync to use bookmark they all are set to sync. I figured I would have a chance to save my home PC's bookmarks before i enabled it on that machine to sync the bookmarks.