How frustrating and disappointing! Agree about trying to get your money back or at least a credit from Frank and Oak, since that is totally unacceptable. Footwear is the endless, almost impossible gamble! You would think that duplication would be a slam dunk, but apparently not :(.
I have lots of fails--it's a part of life! I would say banish the guilt! Buying those things didn't take food from your children's mouths or anything along those lines, so no need to feel bad.