Where Are You McDLT?

Where are you McDLT?
The hot side stayed hot, the cold side stayed cold. It WAS the “best tasting lettuce & tomato hamburger ever”… so where did it go? And, why has it not returned?
{ and, yes, that is Seinfeld’s Jason Alexander in the commercial }
{ btw, to the best of my knowledge the McDLT name stood for “McDonald’s Lettuce & Tomato.”}