It seems that there are some issues to reconnect to a game after a game or system crash.
In a private league match, my game / windows crashed. I couldn't launch the game and had to restart my computer.
My opponent made an ALT F4 to quit the game before the end of the countdown (this is what we do in order to avoid a forfeit and leave the time to the player to reconnect)
When going back to the game, the game had vanished (we could only restart the game)
Some other players from the same league, in almost the same situation had the game set to forfeit. As a commissionner, I can cancel the game and allow them to replay
Some monthes ago, I had tested this possibility of rejoining a game after a crash in a private league environment (where the goal is to play a good game, and not win by a forfeit) :
I made ALT+F4 in order to close the game and didn't try to reconnect at once.
My opponent waited the 6 minutes count down to be in the last 30 seconds. Then, my opponent made ALT+F4.
We both waited for 10 more minutes (discussing on Discord).
Then we reconnected to the game and were asked whether we wanted to restart the game or not, what we did.