How do you know it was overlooked? You seem to be implying the people who VIPed and filled the tank are incompetent. What probably happened is this. The owner of the tank took it to an LDS for a Hydro and VIP. The LDS sent it out to a hydro facility for testing (as most do), where the year was stamped upside-down. The tank passed and the LDS VIPed it and filled it aware of the unique markings. It is funny and good to share to alert divers to double-check the hydro stamps but it is not right of you to imply there is some sort of wrong doing on the part of the dive shop.
Except for the fact this is 2012 and if the tank was VIPed continuously the mistake would have been missed at least 3 times. FWIW I have caught the same mistake on tanks. The hydro facility just fixed it.