I’m really not a fan of buying new bikes in general. There are so many better deals to be had through bike co-op’s, craigslist, facebook and ebay. Just something to consider for any future endeavors.
I empathize with you otherwise, I’ve had my share of buyers remorse and difficult customer service issues when buying a bike. These large corporate sporting goods retailers should be avoided like the plague. Your LBS on the other hand, under the right circumstances, can be a great place to get fitted for a bike.
Im sure the derailleur hanger exists and a reputable bike shop should be able to help.