RROP #17 also says that the deck must be rebuilt in a "fair" manner. IMO it is ABSOLUTELY IMPOSSIBLE to play this hand out fairly. Also rule #17 just talks about the deck stub getting fouled. I think the intention of this rule is for situations where the dealer believes the hand is over either drops the deck onto the muck pile, or begins the wash/riffle/shuffle, or something like that.
I don't think that Rule #17 applies here.
As was stated earlier, it is possible, and overwhelmingly likely that each player saw different cards. When a single card is exposed, it is clearly shown to all players and announced out loud by the dealer. Then the hand continues when ALL players have the SAME information.
In this case, not all players would continue the hand with the same information. The betting cannot continue in anything that even closely resembles fair poker.
IMO, the options are:
1) Distribute the pot equally among the remaining players and continue on to the next hand
2) Declare the betting over, reshuffle the deck, deal the board, and award the pot to the winning hand
3) Leave all 20+ exposed cards face up for everyone to see throughout the hand, and play out the hand (betting and all) with the remaining stub. I think this option sucks, but at least all players would be betting with the same information.
This happened to me a few months ago (where half the deck was dropped ) I went with option 2, as this I deemed this being the most fair. I had no complaints