Dealer reshuffles all remaining cards and the discards before flipping the river

Question

This situation happened. There were three remaining players. One is all in. Two remaining players start a side pot. They look to the dealer to show the river. Problem is the dealer made a mistake, he started shuffling all the remaining cards with the other player's discards. What should have been the outcome?

Answer 1

There's not much that can be done. Dealer should just complete the shuffle, cut, and deal the river card. Yes, it might be a previously discarded one, but the hand is still as mathematically fair to the players as possible under the circumstances.