You are right but he is in TTT Extended edition in some flahback scenes with faramir and denethor that give more information on boromirs relationship with his brother and his father. They look good too. They are obviously set before boromir goes off to go to rivendel to meet the fellowship, this doesn't mean he is back from the dead. The films aren't just a recreation of every bit from the book that wouldn't be very good would it.
Turin is right. The "dream" someone said that Faramir had was not a dream. In the book it was Faramir talking to Frodo and Sam telling them how he found out his brother had died.
These scenes add to the boromir-faramir-denethor relationship. I think if they put it in the TTT to begin with, a lotta ppl would be confused just like u guys were about whether or not Boromir came back from the dead.