I just had this happen last night at a 14u game. We were up 12 to 1 at the time, so it didn't end up being a big deal. The runner at third base was clearly in foul territory and caught a soft line drive which was going over his head. He actually reached up to snag the ball out of the air. Our third baseman was moving to possibly make a play on the ball. I'm not saying that he would have made the play, but he would have been close. The ump just called it foul, and let the game proceed. We did end up winning 12-10. I would assume the runner should be out.
According to the 14U rules here:
The Official Baseball Rules are the first in the order of precedence to specify a rule for this scenario.
According to The Official Baseball Rules
- Rule 5.09(b)3) - A runner is out when ... He intentionally interferes with a thrown ball; or hinders a fielder attempting to make a play on a batted ball
The runner should have been out.