I wish I had read this thread earlier today as I had the exact same issue and never realised that a car collection office for all the major companies is airside - never have I heard or experienced this set up before ! Was in luck was on same day of arrival but had all the agro of rescreening bags and producing documents required . The signage is present but for those of us used to car rental companies office landside in arrivals it just did not register - lesson learned. As a footnote thrifty or as known as Hertz tried their best to upsell a bigger vehicle , more insurance at an astonishing rate ! Not impressed though the car booked was new and nice .