All registered daylilies are in the database. The search just has a harder time narrowing it down when the cultivar is 3 letters or less. Some day that will be updated.
Another way to search is once you are on the Database page, on the right side is a box 'Visit our custom databases'. Click on the daylilies one and and then click on "Browse the full list of daylilies". From there you can go to the 'View plants by cultivar' in the alphabetical listing. Takes a bit longer but at least you'll know where to find it.