This is a rep from Market Force, a mystery shopping company. I do mystery shopping for them. They are calling because they are looking to fill a mystery shop "job" right away. They don't leave a voice message because they are calling a list of people and they will get someone that will take the job. If they left a voice message, they would get a call back later and just end up telling the caller that the "job" has been filled.
Now that I understand their process I know to put this number in my caller ID and call them right back.