Actualy it is tracked.. Just a mod needs to be created to see the database easy.
I made one for ubb 6.5.x and made on for ubb 7.x.
And yes, it's tracked.
I'll be happy to post the code here, but it's messy to say the least, this was early early first php code for me. It also allows you also to delete votes.
There is some stuff surrounding it that will say not enough posts, or to new a user. I used this script to check for illegal votes with a photo contest we held last year. It takes a topic parameter, which I think is the message id from the post with the poll.
Sorry I can't clean it up for you, I have nu running 6.5.x installation to test any changes.
And don't worry about the password in the file, that's from long ago http://www.siemons.org/pollv.zip