I placed a WAV file in Adobe Audition waveform editor (not multitrack). I then trimmed audio. I clicked File - Save — but I meant to click File - Save As. Is there a way to restore the original file (and all the stuff I trimmed? I immediately click CTRL-Z a bunch of times, but I was not able to get it back to the full untrimmed version. I still have Auditon open.
Short answer is no
This is why you should never edit the original version of any file you care about; always use a copy. Waveform view is completely destructive at the point you hit 'Save' (not so much with Save As). At that point, the temp file you are working with gets eliminated, so there are no undo steps available, even though Audition is still open.
Yes it would have - it's non-destructive. You would have to save your edits as a mixdown, but the original would remain untouched.