The umpires clearly made the right call based on the rules as they currently exist, as explained here:
"We felt that the runner going to second base never made it to second base and the runner going to third base never made it to third," [Reds manager Bryan] Price said. "We retrieved the ball and went out there to get the force at second base and tried to get the last out at third base on an appeal." But the Official Baseball Rules book is pretty explicit on this issue with less than two outs. Rule 5.08(b) in the 2015 edition, 4.09(b) in previous versions, states that on any play in that situation with the bases full "which forces the runner on third to advance, the umpire shall not declare the game over until the runners forced from third has touched home and the batter-runner has touched first base."
Okay, but... we know from the famous Merkle Game, perhaps the most famous game in Cubs history, that if there are two out in a situation like that and a ball is retrieved and a runner is forced out because he didn't touch a base he was supposed to, the inning is then over. It happened in a Midwest League game just two years ago, and you can see the team in the field did everything right, not leaving the field, calling for the ball and stepping on second base after the runner coming from first failed to touch second:
Now, in the Reds/D'backs situation, a couple of things happened that would have negated even that sort of play. A security guard (or some other team employee, it's not clear) touched the ball in the outfield. Not all the Reds stayed in fair territory. Even if there had been two out, the umpires would have probably called the play dead as soon as the ball was touched by the security guard.
But what if this had happened instead? Suppose the Reds had all stayed on the field, the ball had been retrieved by one of their fielders (without being touched by anyone else) and they had then touched third base, then second -- since in the video of the D'backs/Reds game, you can see that neither of those runners touched the base in question. Why shouldn't that be a double play? Why do MLB rules allow that sort of base-touching play with two out, but not with one out, as shown in the rule above? Seems inconsistent to me.
Seems to me MLB ought to change this rule so that all runners forced to advance in a situation like that should be required to touch the base they would be advancing to, no matter how many outs there are in that potential walkoff situation. What do you think? Thought you might like to examine this while we wait for tonight's Cubs game.