If GO4 is installed and working, use it. That's the correct DJI app to use with a Mavic 2 aircraft. There's also some 3rd party apps that will work, but as a newbie GO4 is definitely the one to use.
Most likely the battery swelled and popped loose, instant power loss. At least that's my first thought. There's folks on here that could look over the flight data file and give you a better explanation I'm sure.
Been a ham since 1988 and would be interested in how you release the wire. They do make release systems for these, but they're not cheap. Let know when you get time.
KB9BYP