So - I believe I've discovered a fundamental law of software design. It will probably take some more laboratory testing, and maybe some peer reviewed research papers....but it goes something like this:
After 1.5 weeks, all design scribbles lose 100% of their meaning.
Corollary 1: if you have any napkins with software design on them for more than 1.5 weeks - you can throw them away.
Corollary 2: you don't have to feel guilty about discarding said scribbles - though if you have a memory file or developer scrap book folder, it might go neatly in there - as it is cool to say, "oh HEY - here is a meaningless drawing from before we even developed this thing".