The file should be in backup history. First try File>Backup history for <filename>... If that does not work:
The most recent copy will be in your backup path, under your config directory but not the version by default, vsdelta (let me know if this does not make sense). Under there, you will find an "ftp" directory, directories for the hosts under there, and then the whole paths. You will see the whole filename as well as <wholefilename>.vsdelta2 and perhaps some similar files with numbers on them. The one with the whole filename is what you're looking for. Be sure to copy it out of there.