Baserunner interference question

[glengc]

Hi,
I have a question from a game I was coaching. 10 year old boys game, runners on 1st and 2nd, 2 out. Bouncer to to short near second base, my shortstop steps into position to field the ball, the runner on second gets two steps and bowls over my shortstop (would have been a great hit in football!). Ball goes bouncing into left field. The ump standing near second doesn't signal anything and I wait till the play is over till I question the ump about baserunner interference. He said the runner was entitled to two full steps and the fielder was ok to hit. I then asked him to consult the home plate ump and he says the ump at 2nd base was right. I have never heard of any such rule and to me it was a clear case of interference. Is there a rule that I haven't heard of?
Thanks!