Getting my RSVPs back blank!!

Heads up brides who are sending out their wedding invitations and rsvp cards. I clearly addressed my wedding invitations and I put my return address on the rsvp envelope along with a stamp. But I continue to get rsvps back with no name on either the envelope or the reply card. They just checked the reply card and sent it in the mail completely blank! I don't know if others have run into this problem but if I could go back I would write the name of the family on the rsvp envelope so I could avoid this problem. It's a hassle asking around who sent their rsvp in the mail blank and trying to determine who it is.