Thanks very much for everything, everyone. I have downloaded God knows how many file recovery programmes and they all say that there are "blocks" to opening that particular file. This, although I don't know much about it, would seem to fit with Clinton's hypothesis re the scratch. One programme, Virtual Labs, seems confident of saving the files to my computer but wants a hundred dollars first! :[] I went up to uni tonight with the intention of opening (or trying to) the file on the computer I was working on, but another student was working there and I couldn't very well ask her to clear out (I did, however, warn her not to save her file in the floppy drive!!)

Currently retyping my paper. It's not as good as it was the first time, but I suppose it will do.