Who calls back on an unrecognized number with no message left? That's bizarre.
When applying for jobs, there is nothing more irritating than seeing a missed call, getting excited/anxious, and calling back...a #%*@^ telemarketer. On the flip side, I briefly forget that I am unemployed, since all I think about for the next 5 minutes is inflicting the most sadistic forms of torture on every telemarketer that has ever lived.
Seriously though, googling unknown numbers does help.