Hardly a new phenomenon. Back in the day (the rotary phones, a dime at the booth day), I noticed that I knew the telephone numbers of quite a few persons whose street address I did not know; I knew perfectly well how to get to the corner of Easy and Mean Sts., and that my friend lived in the ranch house with the juniper halfway down Mean going west. But could I give you the 100s part of the house number? Probably not. Did it matter? Only if I were mailing Christmas cards.
She could also have given him her boyfriend's email address, which would not have been too much harder than making a phone call. Numbers are harder to remember because it's a string of numbers. Email addresses are easier since the letters form actual words and names.