You are assuming that human trafficking only happens in seedy environments, where low amounts of money are exchanged. SADLY many involved in this are wealthy and a place like Disney provides all the cover that they need. Disney is often the first name that comes up in investigative reporting and discussions on the problem in Florida. It is an international location where thousands come and go daily. The transportation system makes it easy for an individual to travel to a hotel without a car and return to their family easily. These people will pay large amounts of money that would make a room price nothing.
Housekeeping staff can be trained to see all the red flags. One reason we had a huge issue with them is we trigger red flags. We are two or three adults registered in the room. BUT DS#1 is disabled so my room has children's books, hot wheels, plush, etc ... but no registered child. With the key system the hotel knows when you are in your room. They could easily always do room checks when empty, but too often they insist on seeing the room while guests are inside. That is likely because they want eyes on the guests.
A room check can see children's items or clothing but no child is registered to the room. Another trigger would be certain types of small clothing inappropriate for a child. Certain personal toiletry items. Actually having very few suitcases or personal items. Computers, pagers, card swiping equipment. Excessive amounts of alcohol. Any adult paraphernalia. Refusing cleaning and Do Not Disturb Signs.
Disney continuing to do these checks has likely kept the resort less susceptible to the activity. The worse PR for Disney would be for them part of any story.