Double Play Question

[Rev.Ref63]

I hope this isn't considered a "dumb question." I've always taught my children that the only dumb question is a questioned not asked.

My 16 year old son and I love to watch and play baseball. Recently, we were watching a Cub's game and my son noticed during a replay that the shortstop was not touching second base during a successful doubleplay. He was amazed that the umpire called the runner "out" when the defensive player was "off the bag" at second. I told him that I thought there was a "zone" that the defensive player must be in and did not have to literally "touch" second base.

Am I correct about this play or did the umpire on TV blow the call?