Hypothetical Tournament Ruling Question

[Double Ice]

In another ruling, I think with Kenny Tran, someone moved all in on the flop and Kenny called. The other guy mucked his cards but the dealer identified them, turned them face up and ran the board. The other person caught runner runner and won. This doesn't agree with the "nothing happens, he mucked so its dead" so I wanted clarification as to how it works on the river.