Caller left no message. If the message were important and/or if the caller were someone I knew or do/did business with, the caller would have a voicemail. No message? Ipso facto, not important and nobody I know = Telemarketer / Scammer!
I have blocked the number from my phone. I realize this is a futile gesture in the face of an avalanche of spammer calls, but doing so makes me feel better. -- feels kinda like voting, only less patriotic.