d-backs/padres ending

[rulesmaven]

Extra innings. Just ended a few seconds ago. Bases loaded two out, bottom of the 10th, tied. Batter walks. Runner on second base runs from second directly toward dugout instead of toward third. He's well on to the infield grass when the runner from third touches home.

Umpires caucus for a long time. It's unclear whether the runner tried to run back from the dugout to third. Announcers had no idea what the rule is. What is the rule?

(After consultation, they counted the run and ended the game.)

Edit: Watching post-game. Umps still in dugout discussing. Fans have left.