I am not going into a Steam discussion, but instead I will try to offer some help. As long as a game has been properly installed using Steam, some of the games can in fact be started without being connected to the internet. I just tried rebooting my PC with the cable unplugged and I was able to start and run Divinity -Original Sin. What I did was just double click on the game exe file. It can be found in the folder \Steam\steamapps\common\Divinity - Original Sin\Shipping and is called EoCApp.exe. I suspect this hold true for many of the games installed by Steam, since all the files necessary to run the game is installed on your HD. You just have to find which exe file to start. Hope this helps so that you can run and enjoy your games.
