Just to add - I've actually done this before without buying fully-refundable tickets. I dont know about other airlines, but with United, I simply book a same-day ticket to Las Vegas from LA (any cheap fare), and they fully refunded it, as their policy is that any ticket is fully refundable within 24 hours of purchase. I just call them and book it on the way to the airport and cancel it while taking the escalator out of the "security" area.