The paper concerns an identification of rigidity parameters for thin inclusions located inside elastic bodies. A delamination of the inclusions is assumed thus providing a crack between inclusions and the elastic matrix. Inequality type boundary conditions are imposed at the crack faces to exclude a mutual penetration. We consider elastic as well as rigid inclusions and solve an optimal control problem for finding a rigidity parameter minimizing a suitable cost functional. The cost functional characterizes a displacement of the inclusion, and a rigidity parameter serves as a control function. We prove a solution existence of the problems formulated.