Thanks for the thoughts
It's kind of hard to "remain by the boarding gate" when no boarding gate was displayed. And at Glasgow, easyjet may use the "old" domestic area or the international area, so you cannot assume you know where the gate will be. The status changed from "delayed to boarding to closed" in less than five minutes, so unless you had your eye on the monitor every second, you were bound to miss this.
Still aggreived.