Disappearing audio

I made an 11hr single track stereo recording at 32/96kHz that has disappeared. After the recording, I pressed STOP, waited several minutes for Cubase to draw the waveform, and then listened back successfully at various points. I then saved and closed the program.

When I reopened the project, the audio events in the project window were blank, and there was zero activity on playback. Opening the event in the sample editor also displayed a blank waveform. Oddly, under ‘range time’ in the Inspector, the Start & End times are both equal, reading -1 23:59:59.000 with a length of 0:00:00.000.

Windows file info is almost 30GB. I tried opening the file in a few other programs and they all came up blank.

Other audio from other projects is still there.

Any ideas?

Oh yeah, there is a smaller file in the project that is 6.5 minutes in duration that is still there, visually and aurally.