mysteriously missing mxf file

Hi

I've just shot a whole lot of footage as MXF files on a canon HD camera. In one of my folders, the MXF file is missing. So in each of the other folders there are 5 files, but in one of them only 4.

of course that clip is the crux of my film!

i imagine that there's nothing i can do but thought i'd ask just in case.

by the way, i watched a preview of the clip on the camera, so i know it once existed.

thanks
tamsyn