Perhaps it was just an honest mistake on the part of an inexperienced seller. If so, he/she should take it back and refund postage fees. The 12" tessar type lenses are very common and fairly cheap.
Here is the page from the 1935 Wollensak catalog (cameraeccentric.com). The tables says the 9.5 inch is for 6.5x8.5in format. Note where it suggests going up in lens size for portraits.