Mail Fail

We have a mail guy on our floor that's especially friendly named Jack. He knows everyone and everyone knows him. Sometimes we ride the train in together and chat about basketball. Jack really has a way with connecting with everyone. So one day I went over to the mail room with a package I was supposed to send out. I asked the man at the counter if "Jack" was there. He responded with, "what's his last name?" OK... "Jack" is a common name, so there's likely 2 of them that work in the mail room. So I gave him the last name. The guy at the counter looked like the name wasn't familiar. I asked him if there was more than one "Jack." Then he woke up and said... "oh.... Jack!" Apparently, he didn't know Jack's last name even though the guy worked in the company for like 10 years! And why did he ask for the last name if there was only one "Jack" anyway!?