Use the search field in Finder to search for a folder named "Preferences". It won't show up immediately.
Use the "+" sign to add another search criterium, and from the filter type, choose "other…" and then "System files". Set search filter to include them. This *should* turn up the missing folder. Restore to the Library folder in your home folder.
If you're on Lion, and just confused because there is no Library folder in your user folder (it's hidden by default), then just head on up to the "Go to" menu in the Finder, but hold down the Option key. It should let you go directly to the Library folder.