Geometrically frustrated S= 1/2 magnets are of great interest as they do not show classical long range magnetic order at low temperatures and can adopt exotic quantum spin liquid ground states. We recently studied polycrystalline samples of a new geometrically frustrated S =1/2 pyrochlore, Lu2Mo2O5N2 on the MuSR spectrometer at ISIS. The asymmetry data collected may show evidence of fluctuating fields within the sample down to the lowest measured temperatures. However, the data also show evidence for the formation of a muonium fraction within the sample, which can be decoupled upon application of magnetic field. Here we propose to perform a detailed temperature study of the muon relaxation rate down to dilution refrigerator temperatures in an applied longitudinal field of 5 kG5 to fully repolarize the muonium fraction and determine the nature of the magnetic ground state.