When the player does something to INT with the play. Even though it isn't in the rule book, intent is still an item an umpire may use to gauge the situation.

Interesting play recently, 14&U. Bases loaded, 2 outs.
Uncaught 3rd strike, but catcher not thinking, rolls ball toward circle. BR heads for dugout, runners the same; until offense coaches start yelling to run, then they do.

Pitcher runs forward, picks up ball and dives to tag the plate with ball just in time to beat runner from 3rd. I was impressed.