Saying you got a call from this number and they left no message does not give anyone a clue about who called. My post is only slightly more helpful: they called and hung up when I answered.
I got a call about 20 minutes ago. The girl sounded surprised that someone answered and eventually started talking. She said she was from something Green, I didn't catch the name, and that they were a national furnace, heating, and air conditioning company. I told her I didn't need any of those services and I am on the National Do Not Call List and that they should have access to that information. I stated each point as a separate sentence, to which all she could say each time was a robotic, OK. I told her they should take my number off her list, thank you and hung up. It felt like a fake call and she was just trying to come up with something to say because someone actually answered the phone. Very suspicious.