They usually call neighbors, relatives and friends to look for you. Also while your number may be unlisted/unpublished, when you open a credit card and such, if you put your phone number on your application, it in turn goes on your credit report.
As far as the debt goes they talked to you on the phone so now they have 5 days to send something in writing. When you get that, you have 30 days to dispute the debt. You can send a debt validation letter, you could also send a cease and desist letter telling them she is only 15 and to not call or send anything in writing ever again.
It is your choice, maby someone has more insight on this.