The HPV Vaccine is give to young girls as they have most likely not contracted HPV and it prevents them from getting i think quite a few of the strains that can cause cervical cancer (about a 30% chance of developing with these types or something). If you are sexually active and have contracted HPV (please remember this is NOT an STD) the HPV vaccine is less effective. i don't know why they didn't test you for the virus and decided if you could have the HPV vaccine.
I missed getting the HPV vaccine by 1 year (my school year was the last year that didn;t get it) - annoying.
The cancer won't have been developing over the last 10 years, as far as I am aware it is not how cancer "works". However you could have abnormal cells (which looks like what has happened here) and there is a very simply (but not very pleasent) proceduce that will get rid of these. It was good you went for a smear when you did as it could have developed into something worse. Please remeber that having these cells doesn't mean you will get cancer there is a 30% chance or something so dont go panicing!!
Hope this sheds some light on the situation.