I'm not entirely sure, but I think that if you export contacts to the SIM card, you can't find them in a directory, because the SIM card isn't read by the file system. If you transferred the SIM to another phone, that phone would probably list those contacts in the People app as "Phone Contacts," as opposed to contacts associated with your Google Account.
If you want to have access to the exported contacts file, then use the "Export to Storage" or "Export to SD" option, if available.