You haven't flown in a while. Boarding passes are tied to the flight and scanned on boarding. An invalid pass means no getting on the plane. Unless you can generate a valid pass without doing any special deal you've already been thwarted by the simplest part of the security mechanism.
They've done it the last few times I've been overseas. Just part of the normal "let's make sure people don't get confused and don't board the wrong plane" kind of thing.
