Hail is a much underestimated threat. If as pure ice alone, vs hail-rain mix, hail is difficult to detect on radar. The management of radar is important, adjacent storms with rain or rain at lower altitudes could provide some warning, but during the climb the radar scan may be biased towards the climb altitude.
Hail damage can be very severe and not normally detectable on the flight deck, particularly holes or reduced strength of composite structures – nose cone and wing fairings.
A damaged nose cone might affect drag; a damaged wing fairing could affect lift and drag with severe consequences. Also consider other potential hazards - an overlooked CB, windshear, turbulence.
TEM; first avoidance if detected, or reduce the effects if encountered - reduce speed, then manage the results – slow speed, check, inspect, return. Select a safe course of action.
Safety is not about counting accidents or errors, it requires an understanding of how people manage the hazards in everyday operation; just think about the situations, decisions, and actions.
Celebrate the successes and consider what might we learn from this incident.