Called me too but since I do not answer unknowns, I declined it. I then looked this one up on this website (always check unknown numbers here) and promptly added it to my Call Reject list. Thanks for everyone's input on these--very helpful!!
I had the same thing happen just now. I think they want you to get curious and call them back. When you do that, you have now initiated the call and they have your number and know it is active. Scumbags. Don't call them back ever.