There exists a way to recover some of the Chat Archive through a newer Pro subscription feature: Game Rollbacks. Pro subscribers have the ability to roll back a Game by selecting the Roll Back Game option on that Game's Settings dropdown menu . This appears to also recover the Chat Log of the time (only the ~50 most-recent messages of the time, not the whole Chat Archive). Game Rollbacks cannot be undone. Rolling back might be viable, if you need to recover something recently added to the Chat Log (and your Game has not changed significantly since the last save state).