I've nearly done this as well. Late night stop over in Singapore, went to the wrong gate, flight attendent waved me through despite the pass 'not scanning' and it was only a senior person who waved me down to check that stopped me - I was already strolling to the flight.
This is the importance of working right each time. If the digital scanner makes mistakes even 1% of the time, the gate checkers will learn to ignore it when it squeaks.
Also the "not scanning because you are not holding it right" should be a very different error from the "this did scan and no, you are at the wrong gate".
