We analyze a new approach to the vibration of inhomogeneous surfaces whereby surface defects and their surroundings are properly treated as discrete atoms while the remainder of the solid is represented by an elastic continuum of equivalent mass density and elasticity with quantized vibrational waves. Such a hybrid treatment is aimed at describing defect-local motion while fully coupled to collective vibrational waves in a quantum-mechanical fashion appropriate to inelastic gas-surface scattering. We assess how the hybrid model reproduces the response of the surface by following the quantum-statistical moments of vibrational displacements as the collision progresses. The results suggest that the discrete-continuum approach can provide a powerful tool for describing collisional excitation of defect-laden surfaces within a fully quantal treatment of surface motion.