Walkoff homer, decisive run scores but following runner leaves base path

Question

This question is a hypothetical based on the last play of Game 5 of the 2014 NLCS.

San Francisco batting in the bottom of the 9th, score tied 3-3, runners Arias at second and Belt at first, one out. Batter Ishikawa hits a home run out of the playing field. As Ishikawa trots around third, he is mobbed by his teammates from the dugout. In the actual event, he pushed them out of the way to touch home plate, and the game ended with a score of 6-3. But what if he had not?

I understand that a batter who hits a home run out of the playing field must touch all bases in order for the run to count, and if he fails to do so he can be called out on appeal at the missed base. I also understand that if he leaves the base path he is out. But in this case, the preceding runners Arias and Belt have already scored, so the game is apparently won anyway.

If Ishikawa had left the base path before touching home plate (but after Arias and Belt had scored), what would have happened? My guess is he would be called out and the game would be over with a score of 5-3, but I can't find this addressed in the official MLB rules. (Also, would Ishikawa be in the unusual position of being credited with a HR and 2 RBI but no R?)

A comment on Rule 7.08(a) discusses a related case: if the leading runner leaves the base path, he is out, and if he makes the third out, the trailing runner does not score and the game continues. But it doesn't address what happens if the leading runner scores and then the trailing runner leaves the base path.

As another variation, what if Arias scores, and then Belt and Ishikawa both leave the base path? If they are both out then that would make three out. Does Arias's run count and end the game at 4-3, or does it not, and we go to the top of the 10th still tied 3-3?

Answer 1

This has happened before, most notably the Grand Slam Single of the 1999 NLCS.

The Braves and Mets were tied 3-3 in the bottom of the ninth. The Mets loaded the bases, and Robin Ventura crushed a grand slam. He was mobbed at first base, and never touched second. Only Cedeno, the runner on third, actually touched home. Ventura was awarded a single, and the Mets won, 4-3.

Joe left a comment:

Once Ishikawa doesn't hit a home run (because of him failing to touch home), only the leading run scores (as with anything other than a home run or a ground rule double, no runs may score beyond the winning run in the bottom of any inning at or after the ninth).

Answer 2

In the process of answering Brett's question, I found a slightly better answer for this one.

In the MLB Rulebook, rule 7.01 (Regulation Games), there is an approved ruling specifically relevant here, below (g) (3).

APPROVED RULING: The batter hits a home run out of the playing field to win the game in the last half of the ninth or an extra inning, but is called out for passing a preceding runner. The game ends immediately when the winning run is scored, unless there are two out and the winning run has not yet reached home plate when the runner passes another, in which case the inning is over and only those runs that scored before the runner passes another shall count.

While it discusses passing another runner, the concept is the same as abandoning the basepaths. As such, my previous statement was correct - but clarified a bit. As long as the winning run scored prior to Ishikawa leaving the basepaths and abandoning his attempt to score, that winning run counts - but only that run, and the game ends. The only way the game would not end is if both 'outs' occurred before the winning run scored.