Little League World Series

[JC]

I spend my time at basketball, but I dabble in baseball, too. I just had to ask if anyone saw the 3rd base ump in the final game of the LL world series.
First inning I think, and a ball hits fair in front of 3rd base, then foul behind 3rd. Probably the toughest call U3 has. Very hard to tell on TV where it was in relation to the bag when it crossed the line. U3 immediately signaled foul, the 3rd baseman stopped, but then U3 signaled fair. B1 got a triple (on close play at 3rd)that stood after much discussion.
My first thought was that once U3 signaled foul, ball is dead, even if he then realizes he was wrong. What is the rule?
Would have been interesting if B1 had been thrown out at 3rd, to see if the batting team would have been arguing that it was foul.