For those who think that it's just Disney taking this route. Wynn in Las Vegas starts an on property investigation, if a Do Not Disturb Sign has been outside of a room door for 12 or more consecutive hours. They most likely just call the room to see if everyone is ok, and if they suspect a person's behavior is off while talking with them over the phone; probably send security up to the room to further investigate, and to see to it that there's nothing fishy or strange going on in the room itself that may possibly raise a red flag while talking to the guest in the room while the door is open.
Currently, Mandalay Bay is dealing with a class action lawsuit with 450, if not more people suing them as a result of the shooting that happened in a room; on their property. All because they didn't see multiple things the shooter did as red flags. One of those being, having a Do Not Disturb Sign outside of the door for three consecutive days. At no time did they start any kind of investigation, nor check in with the individual who carried out the massacre. They also never sent anyone up to his room to make any sort of contact, that may have led to a quick visual sweep of the room that may have ultimately led to the hotel it's self telling him to leave the property.
Ultimately, no resort, or hotel wants to find themselves in the shoes Mandalay Bay is currently in; and if the people who sued the property win, the amount of money they're going to be forking over is going to be pretty substantial. With 58 dead, and over 500 injured in the Vegas shooting. This is Disneys way of not finding out the hard way that a person who didn't have good intentions for being there did something.