The RHS International Lily Register and Checklist and the supplements provide data through August 2012. The main register covers the period through September 2005 and the remainder period of time is covered in the five supplements.
The quickest way to find a lily in these registers is to use the "Find" feature in your pdf software.
Be warned that these are large pdfs, especially the main register.
It is my hope that making this link easily available here people will use the register to help affirm whether they receive correctly named lilies from vendors.