Question on when a player accidentally looks at the wrong cards

[Popo]

I was recently playing a home tournament when the following situation occured.  The hands were dealt out and the small blind player grabbed the cards of the big blind player's cards thinking that they were his and looked at them.  As soon as this happened, the player realized what he did.  What is the ruling on this?  Is the big blind player's hand ruled dead because he did not protect his hand?  Should the small blind receive a penalty?  Any help would be appreciated. 

[pauld22]

Some discussion on that here