British sailor Helena Lucas capped an impressive debut in the 2.4-metre class at the Miami Olympic Classes regatta by finishing in seventh place.
Robertson missed the final day's sailing through illness
The 29-year-old competed alongside able-bodied sailors and boosted her Paralympic hopes by finishing as the third highest disabled competitor.
"To finish seventh overall in such a high calibre fleet, and after only 12 days in the boat, has been really encouraging," said Lucas.
"I've learned so much this week."
Lucas is bidding to secure the only British place in the event in Athens after missing out on a place in the squad for the 470-class.
A lack of wind meant that the final day's sailing had to be cancelled so the previous three days of competition decided the final positions.
Fellow Briton Allan Smith finished in ninth place in the 2.4m class while Brian Harding was 18th.
The regatta ended in disappointment for Britain's Sonar crew after they had made a promising start to the competition.
John Robertson, Stephen Thomas and Hannah Stodel were in second place after the first day's racing but Robertson fell ill on Friday and could not compete in the final stage.
The captain was replaced but the change of crew meant the final day's result did not count.
The British team, who clinched bronze at the world championships last year, fell to 11th place on the leaderboard.