That's not crazy, it is the "VOIP phone number" which is used for computer-to-computer calls.
These call originators don't have a phone number until they want to call PSTN numbers. Services like Magic Jack, Vonage, Google Voice, Skype, provide phone numbers when the customer pays for it.
VOIP= Voice Over Internet Protocol
PSTN = Public Switched Telephone Network
Same here: caller ID showed CIAVF and didn't leave a message. I don't how these scammers continue to operate when they do [***] like this; they're a category of people that deserve to be told to kill themselves.