Continuity mistake: In the beginning when Dr. Dandewar hangs up the phone, there is an orderly pushing the cleaning cart in the distance behind Ana. When it cuts to the close-up, the orderly disappears with the cart. (00:00:45)
Continuity mistake: In the beginning when Ana is standing beside Dr. Dandewar who is speaking on the phone we see her looking away from him. When it cuts to him hanging up the phone she looks at him and he has moved a feet away from the wall. (00:00:50)
Continuity mistake: When Dr. Dandewar has hung up the phone we see him holding the X-ray in his hand. When it cuts he is holding it with both hands. (00:00:55)
Continuity mistake: When Dr. Dandewar hangs up the phone you can see the phone chord gets twirled up. When it cuts the chord is straight. (00:00:55)
Continuity mistake: When Ana is done talking with Dr. Dandewar she gets to Cora's desk and places her files on the desk. When it cuts the brown file on the desk has moved. (00:01:15)
Continuity mistake: When Ana hands over the file to Cora, Cora grabs the file on the side. When it cuts she grabs it on the top of the file. (00:01:20)
Continuity mistake: When Ana is talking to Cora at the beginning, Ana has her elbow on the counter and her hand behind her neck. Her hand changes positions from shot to shot. (00:01:20)
Visible crew/equipment: When Ana is about to leave Cora she asks her if Cora can page Dr. Dandewar, then she starts walking. As Cora starts talking you can see the boom mic move reflected in the window right beside Cora's head. (00:01:40)
Continuity mistake: When Ana leaves the hospital she approaches an ambulance. As the walkie-talkie scrambles she puts her arm on her hip. When it cuts her arm is down. (00:02:05)
Continuity mistake: The E.M.T.'s legs in back of ambulance when first shown are hanging over the red line on bumper. When they cut to farther shot, The legs are now pulled up more. (00:02:05)
Continuity mistake: When Ana is driving home we see an above shot of her car as she approaches Vivian. When it cuts to Ana stopping right next to Vivian you can see there a far more cars in the background than it was in the previous shots. (00:02:35)
Continuity mistake: When Vivian bites Luis Ana grabs Vivian, and some of Vivian's hair hangs over Ana's hand. When it cuts to Ana dragging Vivian off Luis the hair is under Ana's hand. (00:05:20)
Continuity mistake: At the beginning of the movie, when Ana is escaping from her husband, she crashes into the bath and in the process pulls down the shower curtain and rail. The shot from above shows the curtain rail landing on top of her, but when the shot immediately switches to show to show a close up of her sitting in the bath, the rail appears to be propped up just behind her right shoulder. (00:06:30)
Revealing mistake: As Ana is driving away from her home, when we see her car driving from a shot high above, we see a car crashing in to a gas station making a huge explosion. However the trees a few feet away from the explosion don't move. The shockwave would have made them react at least a bit. (00:09:20)
Continuity mistake: When Ana and Kenneth are walking through the tunnel, as Andre fires at them, Kenneth is standing in the sunlight shining in to the tunnel. When it cuts to Kenneth and Ana bending down the sun isn't shining inside the tunnel anymore. (00:13:55)
Factual error: When the survivors are first in the mall, you can see a store called Roots with a Canadian beaver logo. While the movie was filmed in Canada, it is supposed to take place in the USA where Roots has a different logo. (00:17:05)
Continuity mistake: When Andre is walking alone and gets to one of the mall's entrances he wipes his forehead. When it cuts he is wiping his eye. (00:20:10)
Visible crew/equipment: When Michael is about to open the door where he finds the janitor, there is a close up shot of the door handle where you see the reflection of three studio spotlights. (00:21:20)
Continuity mistake: When they are backing up the truck, it hits the fence on the left side bending almost the whole fence. When it cuts the fence is suddenly intact. (00:41:05)
Other mistake: When Kenneth and Andy exchange via white board about Fort Pastor, you can see a guy chilling on the roof of a building nearby in the background just over Andy's head when he ask " so what's the bad news." He is not trying to get the attention of either Kenneth or Andy. (00:47:28)
Answer: Since it's not addressed in the script or the film, any answer would be speculation. One could be that Luis is just a generally laid back person, and the appearance of a young child he knows is not enough to ruffle his feathers, even if she isn't supposed to be there. He also just woke up, so he could be a bit groggy and not fully processing the situation as quickly as he might normally. More likely, it's simply the way the scene was filmed; the director and actor didn't think it important to show Luis "bothered" by the girl's presence (prior to noticing the blood, of course).