I started this as a comment to kpoehls's answer but the formatting was getting too weird so, FWIW...
I, too, receive vcards as attachments in Gmail.
The ones I receive are .vcf files and the MIME header is, for example:
Content-Type: text/x-vcard; charset=utf-8
So Gmail is capable of handling these if they arrive in a format that it recognizes.
I know Google did not use to support vcard import into the contacts list (e.g. see http://groups.google.com/group/Gmail-Past-discussions/browse_thread/thread/282b44fb77b7bd4a/e36c7e42a1fd49bc) and, although subsequent to this, there was discussion of hcard and vcard microformat support more directly
(e.g. http://googlesystem.blogspot.com/2007/08/google-maps-adds-support-for-hcard.html), as far as I can see this behaviour, of receiving the vcard as an attachment but not being able to import it into the contacts list, is still the norm (e.g. http://www.google.com/support/forum/p/gmail/thread?tid=5dfe5806e1d55063&hl=en).
None of this answers why you didn't receive the vcard as an attachment but it may be worth checking the actual received message (from the 'show original' option) to see if the data has just been ignored because of a problem with the MIME header, for example.
The simplest method to get the details may be via CSV format, as Michael Rose suggests, unless you just want the vcard contents to import the data manually.