Yttrium Iron Garnet (YIG) is a material with extremely wide ranging applications, having the narrowest ferromagnetic resonance linewidth of any known material. Despite decades of experiments on this material, data relating to its full magnon spectrum is sparse, and we have undertaken high resolution measurements of the full spectrum on a 15g single crystal using the MAPS spectrometer. This measurement revealed that there is a magnetic reflection present which is in conflict with the generally accepted magnetic structure, indicating a deviation of the magnetic moments from the cubic direction. Increasing interest in YIG for applications, as well as the correct interpretation of our own inelastic scattering measurements, necessitates a more precise measurement of the magnetic structure of YIG, the results of which will surely have wide-reaching implications.