Unfortunately, the clones are already out there.
Kidnap one off the street and it's a missing person case until a body is found. Destroy the body and she's not even legally deceased until she's been missing seven years (United States). The only way a bystander would immediately know something serious is going on is if they knew there was more than one clone. And if that person is a monitor, and the one considered most likely to file that missing person report...
Like i said, you're not thinking deviously enough.