If he had a disguiser, you would not have seen his name.
Chances are that either you were mistaken or the staff member handling was. I'm pretty sure that someone actually using their disguise doesn't log though, only the user buying it (I may be wrong on this, someone correct me if I am), in which case I am confused as to where the evidence that you didn't see his name and he did in fact have a diguiser equipped came from.