Help me out with the rules.

The throw to Calvin Johnson where he beat MJ on the slant and ran it almost to a TD.

They said the play was not reviewable because the whistle blew the play dead.

Later, on the play where Bush's elbow hit the ground before the ball came out, the Lions were able to review it, even though the play was blown dead by the official; rendering both teams unable to go after the ball. Well, since the play was blown dead, the Saints didn't have a real chance to recover the fumble. Why would the refs automatically reward the ball to the Lions if it was shown to actually be a fumble?

Thanks in advance.