I once grounded a C 152 before an instructional flight. Even if my student has done a full preflight inspection, I always do a walk around the aircraft before getting in mostly looking for things hanging/dripping/loose.
This time something didn't look right on the horizontal stab. When I looked closer I realized there was a faint diagonal spanwise crease. When the engineer looked inside he found the spar was kinked
. The damage greatly decreased the structural strenght of the tail.
Nobody fessed up but three flights earlier a dual spin lesson was flown (the spin is a required exercise for the Canadian CPL flight test). Knowing the instructor in question I am sure he grossly abused the aircraft with a over the redline pull out.
The bottom line is simple. If you think you have hurt the aircraft
you must report it. Even small bumps can manifest themselves in major hidden damage which often will not be obvious on an external inspection.