Induced effects in the photodetached electron spectra from a diatomic negative ion (H$_{2}^{-}$) near a hard surface are investigated. A $z$-polarized laser is used to knock off electrons from H$_{2}^{-}$ in the vicinity of a hard surface. Theoretical imaging method is used to derive a generalized modulation function for the total photodetachment cross-section, which describes invisible oscillation. It is found that the hard surface strongly affects the detached electron flux as well as total photodetachment cross-section. There exists strong dependence on the distance of H$_{2}^{-}$ from the hard surface and also on the separation of atomic centres of H$_{2}^{-}$. Unlike the detached electron flux, no visible oscillations are noted in the photodetachment cross-section.