Kitten Question

[SympliG]

Hi everyone...i'm new here because i'm a bit concerned about the kitten I just got.
A friend of mine adopted a kitten a week ago and when her landlord found out, he made her get rid of the kitten. She asked if I would be interested in taking her and so I did. According to the paperwork from adoption the kitten was given her shots, was spayed and micro-chipped on 7/2/08 and recieved her rabies vaccine on 9/6/08, the day of adoption. It says she was dewormed as well. Well she was dropped off to me today and while she was laying on me I noticed something small and white on her anus, looked like a piece of rice. I immediately grabbed a tissue and wiped it and when I inspected the tissue it moved, giving me the indication that it was a worm of some sort. I thought hmm, its only one and the paper says she was dewormed so I didn't think much of it. Later on in the night, she was playing on the couch and I saw the same thing.
I am definitely calling the place that she was adopted from to find out about this but figured I would come here and ask about this. If she had been dewormed on 7/2/08, can she still have worms?
Thanks for your help.