difference in playback and mixdown from original capture and edit to next day

Was working on my demo, which was part remix part vocal add-in and overdub. I used my M-Audio FastTrack to capture an audio stream and record my microphone pick-up, which resulted in a stereo track that on the left was microphone and the right the audio stream off my phone. Which was fine because then I just copied that, pasted it as a new track and flipped the channels for the full experience, began my remix and editing work from there and it was sounding awesome. So that morning I got through editing and effect-ing what was gonna be my first track and my plan was to cut and upload the next day. When I went to mixdown and cut that selection the next day, even before that, just proof-listening to the selection, my stereo channels weren’t playing in my headphones the way they did the morning I originally recorded it and edited it and was very happy with it. One of the channels wasn’t even coming through the headphones at all. All that I can think changed was putting my computer to sleep. Closed re-opened the files still couldn’t get back to how I had it. Anyone have any advice on how I can get it to play back the way it did originally that morning, and hopefully rip a mixdown of that as well just how it sounded that morning? If it helps, the file also has a mono mic track and another stereo track on the bottom. Can provide screenshots if necessary. Whoever reads this, thank you for the help.

If you inverted copies there will be destructive-interference: the waveforms cancel each other out. That can make a track disappear.