This incident was covered in a 'Battle Stations' programme on the History channel and had loads of pictures and an interview with the pilot.
It was said that the underside acts like extra wing area providing lift.
The pilot said that he was unaware of the full extent of the damage until he landed and had he been aware then he would probably have used the bang seat and parted company with his bird.
Lucky man whatever somebody must have been looking out for him on that day.
John