I think you may be snookered - I didn't think that you can save a whole address book as a .vcf file (at least I have just had a go and it would only let me export one record at a time!).
How exactly did you save it? In theory it should be possible just to reverse the process to get it back!
You could try this open the address book and go File>import>business card and point the wizard to the saved file(s) on the external drive.