If you've truly lost your repo, with no backups, then yes - its gone. There's no magic that can restore truly lost data.
So, if you have a working copy from someone, you can create a new repo and add the files to it. You lose all history (obviously) but history has already been lost.
You could send the hard drive off to a recovery company to try and get any data restored. Once you have the repo (or at least the db/revs and db/revprops directories), you can re-create the repo from them (by copying them to a new repo's directory). If it turns out you don't have the entire db then things will be a bit more tricky, but its still possible to restore the rest of the data - you may have to send it all off to collabnet and get some support from them to restore the mangled data files into a new, working repo.
Now, you say "svn export" from someone with the most recent update.... that suggests the person has a backup copy that you can export from. Is this the case, or were you confusing it with a working copy?