Audition File disappeared apart from last 5 seconds?

You may not have done anything wrong at all - it looks a bit like a manifestation of the 'delete' bug that's supposed to be being fixed. The clue here is that in your first screengrab you can see a waveform, but no spectral data. What this implies is that there isn't any actual audio present, apart from the last five seconds, anyway - the visual waveform display is provided from the .pkf file associated with the wav file. Do you have an original copy of your file still?

There is another thread about this bug here that you might like to peruse... TBH, I don't know exactly what's going on with this bug at all - there are confusing reports now. As far as I'm aware, the current beta version doesn't do this, so you might be better off using that for the time being.