Sorry to hear that but not surprised.
This was my recurring nightmare on London tickets out of Saigon when I was Gold (which generally booked into L). This was the only benefit I was looking forward to as Diamond and of course I only got to use it a couple of times before it was taken away.
Anyone would think that L is some sort of heavily discounted promo ticket. I'm finding L tickets much more expensive than they used to be, with EVA making wider use of V/R.
What an arrogant lot we have running Evergreen Club!