I don't have a problem with grounding Tyler, but I do feel that a grounding needs to be proportionate to the misbehavior and avoid any unintended severity. If I knew he would miss the game and meant for that to be part of the punishment, I think I would have told him that upfront so he could weigh that in deciding to opt for grounding. Perhaps Tyler himself should have realized this consequence of his grounding, but he is only 11 and probably was eager to escape the immediate unpleasantness of a spanking.
I'm not going to yank him out of his game, but he will have to suffer the consequence when I get home, which is a very thorough spanking. After he calms down, he and I will discuss the details of grounding, including what constitutes a reasonable length of time for a particular offense and what happens if something unexpected comes up during a grounding. He has to understand that grounding is meant to be just as unpleasant as a spanking, albeit in a different way, and that he must expect to miss out on some fun activities if he is grounded. We'll discuss the difference between a major activity such as a game, where others depend on his presence, or an activity that is special, such as a birthday party, and something merely fun, such as going to the movies with friends. We'll agree on whether being allowed to participate in an activity during grounding requires some additional penalty, such as extending the grounding or taking a spanking.