http://www.harrahs.com/wsop/rules.html
Rule #10 WSOP Official Rules
http://www.homepokertourney.com/rules_poker.htm
Check this one out, has a bunch of different rule books
However, this all comes down to the fact that this is played at a home game. The house can choose not to follow these rule books. Also, was it NL tournament or ring game. It's common not to have to show in a ring game. They don't show the cards at Poker Stars unless it's in a tournament