Recently the 5d transition metal oxide Sr2IrO4 has attracted much attention due to its close analogy with high-Tc cuprates. A hidden broken symmetry phase, which is similar to the pseudo gap phase in cuprates, was found by second harmonic generation experiments. It was suggested that its properties bear the symmetries of a magneto-electric loop-current order. We propose to study this interesting phase by performing zero and longitudinal field muon spin relaxation experiments.