Sadly, the Mooseburger is no longer on the menu at the Portal Store. Doug had to remove it because, with the limited grill space, one Mooseburger order with the double beef and bacon took up half the grill while regular burger orders waited for space. It's a very small kitchen. The chicken salad is also history as well due to the numerous components that went into it.
That's not to say that the Moose can't get a Mooseburger - exceptions are made if there is grill space, but you just won't find it displayed on the menu any longer.