I'm usually pretty careful about saving everything and filing it all away neatly so I don't lose anything, but I had a long break from my computer a while ago, and when I came back to it I had a look at some of my old work-in-progress renders and found an image I really liked, only to discover that somehow the upr/ufr files were missing. It's a horrible feeling, you have my sympathy. I decided I liked that particular image so much that I'd try to recreate it, which I thought initially would be impossible (I don't usually have a clear idea of what I want to do when I start a new image, and even when I do I usually end up with something completely different), but actually, not only did the determination to rediscover the image keep me focussed, but all the effort ended up with a much improved result, which I now think is one of my best pictures... ...so don't lose heart, you could try to recreate it and make it even better the second time. Best wishes, Simon.