Received a call from this number and no message left.. unable to identify who called

The caller asked by name for someone that used to live here. When I told her that that person no longer lived here, they immediately hung up without a word - no thank-you or a good-bye.

I didn't have the time to answered but leave no messages.   Unidentified.

Got called twice, left no message.
It happens to be census time. Haven't filled it up yet and I got a couple of cards on my door so... Government agency related?

Answered but they hung up.