Excellent article here on handball, which by extension would apply to a situation "in the box."
http://asktheref.com/Soccer/Referee/Articles/7/Quoting part of it:
"This means that is not, I repeat not, a foul if the ball touches a player's hand. It is only a foul if the player intentionally handles the ball. "
and
"Let me also emphasize that nowhere does the rule book say anything about whether or not the player gains an advantage by the ball hitting his or her hand. In other words, even if the ball were to hit a player's arm and drop right at his feet or even were to go directly into his opponents' goal, these are not fouls if they were unintentional acts. Apparently, I am not the only one whose feathers have been ruffled by years of bad calls by referees and undeserved abuse from fans. As recently as 1996 FIFA specifically changed the laws to make it very clear that it is only a foul if the player handles the ball deliberately. "
Unfortunately I've seen this called just as the original post stated.