I don't think this is possible unless Mac was forcibly shut down, then it's possible for corruption to appear, but even so you should be notified of possible breaks. I recommend use the Spotlight function to look for the application. Go to the Applications folder and look for the software because it might be there, but if it's missing, try installing it again and repeat the procedure, but this time sample something instead of working full time.
I believe this was a simple corruption error since the software disappeared, but as I previously said, this has a low chance of happening.
Anyway, you can always ask for help the developers at https://support.apple.com/final-cut-pro
