What happened was that, due to a glitch in some new software that Cabela's put into use on 1/1/2013, the excise tax on medical supplies was incorrectly applied to some purchases made there. There is no medical excise tax on sporting equipment, and Cabela's has since corrected the error and refunded the money they collected (or at least offered refunds). It only happened on that one day before they caught and corrected it, but that was enough for internet rumors and chain letters to get started.
snopes.com: Medical Device Excise Tax