I had an x-ray done a few years ago and one of the things my doctor said was that you have broken a couple of ribs in the past, i replied no, i have never broken a bone in my body. The doctor then showed me the x-ray with two healed ribs. I said to the doctor are you sure thats my x-ray and she laughed. She asked if i had evet been in a car crash or any other accident, i said no.
To cut a long story short, different people have different pain endurance.
Having joined a boxing club in my teens, is probably were i got the injury, but i went on with my normal life without noticing, apart from the first few days of pain of being punched in the body.
Hence not everyone is a weakling like the guys criticising Hasan on this thread.
By the way, i discovered this 25 years after the incident occurred!