Just to make sure: You can just not click on the notice, and when the opponent finally comes back and does something, the notice will go away. So this is not a 'forced' resign.
In addition, if your opponent resigned (as you described), then this seems like nothing you can do about. He may have realized that the baby needs more care at the moment, making it an unsuitable time to play Dominion.
If you are arguing that the notice is taking up space on the screen and interferes with you for example studying certain card texts or fiddling with autoplay options, then you have a point IMO.