Actually, the retro-rocket package that was at the bottom of the capsule's heat shield was intentionally left in place - and not jettisoned as required- for re-entry. It was felt that the straps that held it to the base of the capsule would also hold the heat shield in place.

My family knew the Mercury Astronauts and their families. Dad was the C.O. for all military personnel detailed to NASA, and was the head of the Astronaut & Training Program.