"Op on finger"

I came into hosp on the 25th sept 2012 for an operation on my finger to have a pin inserted ..I came in at approx 7.30 .. My surgeon explained to me he was going to put a pin in my little finger ..I signed the forms and had the op ...a week later I went back to hosp to have the bandages removed to be told hadn't been able to put the pin in due to me being given the wrong forms and so he did a totally different op and cut into the front of my finger leaving another unnessasary scar and I would now have to have another op in a few months time. The op on the 25th left me with a bad infection and lots of pain. I feel I should never have had this op as I found it so unnessasary and it really should have been postponed. I have been left with a deformed finger and a very painful finger. Why do mistakes like this happen ???