To elucidate the origin of the multistable orientation of a bulk liquid crystal on highly symmetric substrates, we have studied the molecular orientational order in the surface monolayer and the resulting bulk orientation on mica plates. The bulk orientation arises from a coupling of the nematic liquid crystalline order (which has no preferred in-plane orientation at the substrate surface) to the non-nematic surface-induced order. We find that small variations of the tilt distribution of the surface molecules cause in-plane reorientations of the bulk.