Scanning probe Microscopy (SPM) represents a powerful tool that, in the past thirty years, has allowed one to investigate material surfaces in unprecedented ways at the nanoscale level. However, SPM has shown very little power of depth penetration, whereas several nanotechnology applications would require it. Subsurface imaging has been achieved only in a few cases, when subsurface features influence the physical properties of the surface, such as the electronic states or the heat transfer. Ultrasonic Force Microscopy (UFM), an adaption of the Atomic Force Microscopy (AFM) contact mode, can dynamically measure the stiffness of the elastic contact between the probing tip and the sample surface. In particular, UFM has proven highly sensitive to the near-surface elastic field in non-homogeneous samples.In this paper, we present an investigation of two-dimensional (2D) materials, namely flakes of graphite and molybdenum disulphide placed on structured polymeric substrates.We show that UFM can non-destructively distinguish suspended and supported areas and localize defects, such as buckling or delamination of adjacent monolayers, generated by residual stress. Specifically, UFM can probe small variations in the local indentation induced by the mechanical interaction between tip and sample. Therefore, any change in the elastic modulus within the volume perturbed by the applied load or the flexural bending of the suspended areas can be detected and imaged. Such a power of investigation is very promising in order to investigate the buried interfaces of nanostructured 2D materials such as in graphene-based devices.