Hang up on my cell phone.  I called back (*67) and got a message that the number was not in service.  It actually sounded like a recorded message from a typical home answering machine with an unprofessional sounding voice (and as a bonus, it was repeated in Spanish).  An unblocked call back would likely have resulted in the "scammer" getting your number.

"If you're not Part of the Solution, you're part of the problem"

Called me, rang twice, no message left, caller id "unknown."

Called me, did not leave message