Ideas and suggestions.

The host accidentally presses the "Restart" button. He has no restarts left, and the opponent didn't request a restart. The opponent can't do anything about it. There's no save. It's impossible to prevent.

When "Start over" is pressed, the game asks, "Are you sure you want to...?" Therefore, after that, you still have to accidentally press "yes." Similarly, you can accidentally exit to the main menu (and if Red does this during Overlord's Hour, there will be no saves either; and, as far as I remember, when a player exits on the first day, the game doesn't offer to save).

Therefore, in my opinion, an incorrect press of "start over" should be equated to an incorrect exit from the game. That is, it should be treated as conceding defeat.

If a confirmation is added on the client-side, it will slightly slow down the restart process (both players will have to click somewhere during the restart). At the same time, the possibility of accidentally exiting the game will still remain, and confirming that would be ridiculous. Therefore, I'm not sure if it's worth doing.