There are two lists in the drop-down list in the design browser window. The first list (the long one) contains all templates for which matching stationery products are available to purchase from the designers (invitations, save-the-dates, etc.).
The second list is all templates that do not have matching stationery available.
If you don't find the template you want at first, make sure to scroll all the way down to the second list. You will likely find the template there.