I love how passionately ya'll are taking this debate, but i think i've got enough info to cover the situation in the future. Yes, its a cash game and we didn't have a dedicated dealer. I don't expect everyone in a rotating deal to be scooping up cards the second they hit the felt. Maybe in a casino cash game, the dealer would have gotten the cards in before the realization set in. But at the same time I'll clarify: it's wasn't like the cards were thrown down, and then the dealer went and had a sandwich. yes the player with 9's made a mistake. yeah if it turned into a pattern we could start to get tougher on tabling cards versus mucking face down. But, there was enough time to correct a mistake at a home game between friends. i think it comes back to the comment where ruling in the best interest of the game makes sense. the only angle would have been the 9's losing on a technicality, which if he was pulling shit all night maybe we would enforce, but in the end it was solved in probably the best way it could have been.
I do really appreciate all the insights and spirited discussion though!