The phonon emission due to the inelastic scattering of a thermal helium atomic beam from a thin neon layer adsorbed on silicon(100) at 1.5 K has been measured. The energy transfer from the beam to the neon layer is larger than to the bare Si surface. After starting the beam we find an initially large signal which then drops down in a time-span depending on the neon film thickness. We interpret this as a collision-induced desorption, or sputtering, of the neon film. The data suggest that neon on silicon in the first monolayer desorbs more easily than neon on neon in a thicker layer.