As repeated many times on many threads, even other forums, there is no records kept on which athletes were tested to what degree. None the less, by deductive reasoning based on the amount of races entered, and won, where most testing occurred by percentage, during Lance's main years of racing it would be virtually impossible that he was the most tested cyclist, with Mario Cipollini, Erik Zabel, Laurent Jalabert, and Robbie McEwen likely tested many more times, and a few more racers tested more as well (Simoni, Heras, etc.). Lance simply didn't races as much, nor win as often across the calendar year as they did. And there is zero indication or proof that he was targeted for out of competition testing more than any other cyclist.
In the last 3 years, testing frequency has increased in the sport. None the less, since his 2009 comeback, it's still not likely Lance was the most tested athlete last year. Logic would indicate that cyclist was Mark Cavendish.