In my opinion...
* It is possible MAM checked into the hotel earlier, prior to picking up Shaniya. Therefore, he would already have had the key, so it would have been unnecessary to stop by the front desk with her in his arms. With the key already in his posession, he could have carried her from the car directly to the elevator, and then to the room.
* Another possibilty... someone else ( an as yet unknown person to us)actually booked and checked into the room. In this case, the person who checked into the room would only have to call MAM and tell MAM what hotel and room number. Then MAM would have had no need to stop by the front desk at all, just carry Shaniya directly from the car to the room. The other person, waiting in the hotel room already, would answer the door after hearing MAM knock, and let MAM and Shaniya in the hotel room.
* In defense of the front desk attendant (I work in a hotel), he/she may not have even seen the news reports until much later. (Most places of employment do not allow their employees to watch tv while on the clock. I know that when I get home after working all night, I get home and go to sleep, I don't watch tv). After finally seeing the news reports, the hotel employee may have gone back to the hotel, told their manager, reviewed the videos, and then called the authorities.
I hate to condemn the hotel employee for doing what was right- calling the authorities and alerting them to the existance of the surveillance video. I'm going to give this person the benefit of the doubt, and guess they alerted the authorities as soon as they realized they knew something of importance.