Now why did I throw this away?

I once read the following anecdote about John von Neumann’s housekeeper (the only reference I found was, of course, on mathoverflow). Being asked what her impression of him was she is said to have replied that he is quite a nice man and all, but that she did not understand how he could get any work done; after a long day sitting at the desk writing he would just throw everything he’d done in the garbage. I thought Doron Zeilberger (unfortunately, I cannot find the opinion I was looking for — any help appreciated!) in one of his wonderful opinions pointed out that nothing would be greater bliss than to get our hands on all the failed attempts that von Neumann made. What we could learn from his mistakes!

I spent last weekend in Boston and for a bare half an hour worked on a proof that has consumed most of the last 3 weeks. The proof for the little piece I was wokring on didn’t seem to go anywhere, so I threw it away. Now, having written up what I can prove so far I yearn to read what I read back then — the modifications I made TeXing my progress just now remind me an awful lot of what I wrote on that piece of paper. Now why did I throw that away? Or better yet, why on earth did I write on a piece of paper instead of my moleskine? Damn.

Update Fred was kind enough to find the correct Zeilberger post for me: