There are two possible ways to answer this question.
First, you can argue that no one represents the people who do not vote. Those people have not made their voices heard and therefore they are not really represented by the people who are elected to represent their district, state, or country.
Second, you can argue that non-voters are just as represented as people who vote, particularly those who vote for the losing candidate. When politicians take office, they are not just governing for those who voted for them. It would be irresponsible and unethical to do so. It would also be very difficult. Let’s look at the example of the tornado that just hit the Oklahoma City area. The federal government cannot possibly go through and give disaster relief only to those who voted, or to those who voted for President Obama. The government officials are, in that case, representing all of the people who live in that area when they order relief efforts to be undertaken.
Thus, it seems more reasonable to say that the people who do not vote are represented by members of Congress, by members of state legislatures, by governors and by the president just like everyone else is. There is no real way for government officials to act only on behalf of those who do vote.