Mine rang once also - however, I read about a scam where people hit call back and it goes to an offshore account that then bills you hundreds of dollars for "services". Basic rule, if was important, the would leave a message.
Michigan call - rang short and stopped, no message left. I blocked the number so it will not ring to my phone anymore. As far an calling and opting out like the one person that is just confirming that is an active number and now you might get more calls....I just block the number after I GOOGLE to see who it can be.