If Bex is that intelligent, then how would she do such a silly mistake? She is telling the guy that she is back, so the guy saw her face before and remembers her, so he wil easily give her description to the police. Right? The whole point of the girls disguising is to avoid having their decription picked up by anyone around, but if they simply go to the guy and tell him: "hey, here I am, you know, you got my description...." then the chances that they'll get caught in a day or two are high.