Woe betide failing to keep those plant names under control. In order to remember the name of that lovely purchase you can stick the label in along with the plant. The most tasteful labels seem to get ripped off by the wind or weathered by rain to smudged-out blankery. Many nurseries give out the loudest of labels to swing from the plant and introduce a note of the fairground.
I have tried every which way of keeping a note of what I have bought or drooled over in a nursery with a view to future ownership. The two-fold attack is the best. Keep a little notebook. Take it everywhere and scribble down brief notes. Always include the date and where you were. Photographs are one thing but will clog up your computer and fail to embed the idea of the plant in your memory.
For back-up, get yourself a small plastic box with a card index and file all purchase labels away. Get an indelible pen and mark on the dates. Remember too that the scientific nomenclature has a habit to trip up with name changes.
No record and forgetting the name is bad news. I have been trying to track down the showiest but ungaudy oriental poppy for a year or two. Narrowed down to flowering time, I caught up with it yesterday at Beth Chatto's nursery. This is is Papaver orientale 'Juliane'. I would elbow 'Patty's Plum' and 'Sultana' for it.