Not Baseball: Challenges in the NFL

Sorry for the off-topic, but I figure there are a lot of NFL fans in the crowd here and Giants fans in particular. Anyone who watched the game on Sunday (and who is not subsequently blocking out the pain) saw the play toward the end of the game where Vick dove forward instead of sliding, and the ball appeared to pop out of his hands. Why was there no challenge? That was the question on my mind, and on the mind of many of the callers today on WFAN.

You'll see the highlight of the play in question at 3:39 on the video:


The common wisdom among the callers and the hosts - some of whom stated this as gospel - said that the challenge HAD to come from the booth because it was within two minutes. Because of this, Coughlin couldn't challenge, and if it wasn't reviewed, it was because the booth decided it wasn't close enough to review. End of story.

As a lawyer, this didn't really satisfy me. Is the rule that the coach can't challenge within two minutes of the end of a half? Or can he not challenge plays that BEGIN after the two minute warning? What about a play - like in this case - that begins before the two minute warning, but where the part of the play you want to challenge is AFTER 2:00 has passed? My understanding was always that if the play began before the two minute warning, it was on the coach to challenge the play. That's a nice, bright-line rule.

So I tried to look up the actual rule. A quick glance at the NFL Digest of Rules didn't shed any light on the topic for me. I'm sure there is a copy of the NFL Rules out there somewhere on the internet, I just don't know where it is. Secondary sources had the issue equally confused.

Wikipedia: Plays inside the two-minute-warning, and all plays in overtime, cannot be challenged; any review of that play must be initiated by a replay official off-field

eHow: The current system allows coaches to challenge on-field calls in certain areas of play before a new play begins by throwing a red flag, as long as the game is not within the last two minutes of either half.

I think Wikipedia's definition is more accurate. But what do you guys think? The closest I could find for an answer was in a footnote near the bottom of this NJ.com article by Mike Garafalo (who seems to be doing a pretty good job):

I had one e-mailer ask if Vick fumbled at the end of his 22-yard run. No, I don’t believe he did. He was down with the ball in his possession and it only popped loose when LB Michael Boley fell on him. That’s down by contact right there. The e-mailer also asked me if it’s up to the booth to review the play because it ended at the two-minute warning. No, the Giants would have had to challenge that play because it began outside of the final two minutes.

It may be, of course, that Vick was down by contact, making the whole issue moot. I can't find much aside from the above quote discussing the issue, despite the fact that it was on talk radio all day. Is that because nobody actually knows the rule? If that was a challenge which was incumbent upon Coughlin to make, and he didn't, I'd imagine there would be a ton of outrage, even if it was an unlikely challenge to win.

Baseball is my sport, not football -- can anyone help me out? What is the exact rule on challenges? Did Coughlin screw up?