Confused after colposcopy

Hi everyone, I hope you can assist with some advice. I received the results of my yearly smear test and it came back negative but with high risk hpv. I was referred for colposcopy which I had today. During the examination they found abnormalities and took a biopsy. How can the smear come back normal and these cells be discovered? Also as we were going through my notes before the procedure we were discussing my previous diagnosis of CIN 2 on 2006. This was removed with the loop. But in 2005 I had shown up high risk hpv? I was not told about this at the time.