I'm going to respond on the questions you posed and then I'll provide my opinion on this type of situation.
1. "Why didn't the surveillance operators notice the guy?" My guess (and it is only a guess from experience) is that the surveillance operators see this scenario on a daily basis/ daily occurrence. You cannot imagine how many drunk people come in to an ER and pass out. This is not the only location they are monitoring so if other things are happening within the facility, their focus may be on that. Many times, the operators will not bring up a camera unless there is a situation going on so that they can focus on other areas of the facility such as the parking lots.
The security staff on the other hand should have noticed the guy bent over in his wheelchair PARTICULARLY if they thought the person was intoxicated and sleeping it off. Why? Because that is how some drunks die... they restrict their own airway, choke on their vomit and smother in their drunken stupor. So I blame security staff for not being more vigilant in their patrols. Mind you, it is not rare to have people waiting hours upon hours in an emergency waiting room. People think they should go to the ER because they have a tommy ache. The key word here is that it is an "emergency" room... not an alternative to your regular doctor. (sorry, that is a sore spot for me.) People are seen by medical staff based on medical priorities and/or, what happens to come in by ambulance. Consider medical staff shortage, real emergency medical concerns i.e., heart attacks, etc. or a sudden rush of patients with severe traumas from an accident which often dictates priority, medical focus and adds to the wait time.
2. "So what is the right way to do hospital security like this?" Security staff patrols assigned to ER/waiting room should be familiar with the people in those rooms. The admission clerk and the Security Officer should be communicating concerns.
In this particular situation, the ER staff were alerted to the man in the wheelchair (and it appears) yet did not check on the man. At the bare minimum, the clerk should have asked the Security Officer to check on the man at that point. As you can see from the video, the Security Officers stood around quite a bit. It's called "patrols" not "stand-arounds".
3. "Are the guards at fault for failing to notice?" Yes, they should be ALERT to everything. They were too complacent in their duties.
4. "Or should the nurses have been checking more often?" Yes, they should have checked on the man, or they should have communicated to someone else about the concern and had them check on the man. When the man's name was called (was it?) to be seen by the nurse, she should have walked around the waiting area to ensure the person had not fallen asleep and not heard her/him, checked back in a few minutes to ensure the person had not gone to the bathroom or out for fresh air, etc.
5. "Or something else?" Working in a medical facility like this requires teamwork and communication. Security staff should always be aware of potential problems, and should make it a point to check in with staff to ensure everything is okay. Medical staff should depend on Security staff to assist them not only with patients but possible issues with visitors or suspicious activities. They should be encouraged to alert staff of concerns and not brush those concerns off because it "may be nothing". Better to be safe than sorry.
Establish a facility-wide communication that encourages staff members to alert security to any and all concerns. This is very important for a security program. Security staff cannot be everywhere and encouraging medical/non-medical staff members to be their eyes/ears will help in keeping the facility safe and secure.
As a former Security Manager, I know the up time and down time of staff... many times I sat down for 30 seconds at lunch and had to run to a call or barely had time for a bathroom break. But also many times I ate my lunch at a leisure because it was so quiet. With respect to this incident, I sincerely hope that the security program and the ER admissions procedures were re-evaluated to ensure this type of incident does not occur again. There are a lot of lessons to be learned here that can be taken and placed in other parts of the facility. As far as I'm concerned, it turned out to be a wake-up call for the Director of Security and the Nurse Manager of the ER.
Sorry for the long post.