if it were me, i'd start asking questions that if it was something real and valid, they'd know.

say if someone told you they went to meet a moviestar at the theater last weekend, and they watched the film with them.... i'd ask what film it was, and who the star was, and i'd check it up online. was the movie even playing that weekend, is that person you mentioned in the country, it's a sure way of knowing

facial expressions help too