External Hardware..was it corrupted??

I was just listening the music since this morning, from my external hardware,with the use of my laptop,when suddenly I pullout my external hardware,without knowing what would happen to my files in my external hardware.This afternoon,I try to use my external hardware(160 gega),I wonder why I could not see my files in my external hardware.I try to see the properties in my external hardware,but it is already full..how could this happen??I still have almost 100 gega free space this morning??then I go to my friend and tell him what happen..he said..you know you have to reformat your external hardware,and you gonna lost all your files because your external hardware was corrupt and for reformat...ohhh..so sad..but some of my files was still in my PC..what about the others..movie..music..oh..I think my friend here has a copy..do you have it,I ask him?..no probs friend!!I still have it and you can have a copy of it..I said..thanks..instead of being sad..I was still a happy man today because I can still put back my old files in my external hardware..Next time,I will not remove my external hardware,without an advise that device or USB is safe to remove.It was a great lesson on my part.