Another way of taking attendance: Since your life vest has your cabin number on it, they take attend

Ok during muster drill ....how do they know if you've left your cabin or not, I've been curious about that since my very first cruise? Do they have hiden cameras in your cabin or something, every cheat for habbo hotel do they go and check every cabin to make sure they are unoccupied during muster drill. Really how do they know?
They take attendance at the muster drills. On the older ships, they call out each cabin number and you say, "Here" and mark you as there. On the newer ships like Oasis and Allure, your key card is scanned when you enter the room where you're assigned, so they know that way. Sometimes, stewards find out who is not at the drill and will go and knock on doors to see if anyone is in the room.
If you are not at the drill, depending on the cruise line, they request (insist?) that you attend a make-up muster drill with others who were absent. Obviously, it's very important that everyone attend a muster drill in case of emergency.
An elderly couple was just kicked every cheat for habbo hotel off a Back-to-back cruise because she was sick and didn't attend the second drill. I think it was a big faux paux on the cruise lines part to just kick them off without accessing the situation. Nevertheless; it shows you they take missing a drill pretty serious.
Another every cheat for habbo hotel way of taking attendance: Since your life vest has your cabin number on it, they take attendance that way, too. One of the crew has a clipboard and is checking off cabin numbers on their list. Then they'll every cheat for habbo hotel often call out just those cabins not checked every cheat for habbo hotel off on their list.
I've done it several ways for "taking attendance" on the muster drills. Back when life jackets were required at the drill, they looked at the back of the life jacket, near the neck, where it had the stateroom number on it. On my last one, where life jackets were not required, every cheat for habbo hotel I think I either just gave the attendant my stateroom number, or showed my SeaPass card, and the attendant checked it off of the list.
We have been on 9 cruises and never once have they scan our cruise card or call out our names. Also two of our cruises we were not require to take our life vest, so we are also wondering how do they know. We have been on 3 back to back cruises and were only require to attend the muster drill the first day of the first cruise. On the second leg of our cruise we just walk around the ship while the new people went to the muster drill.
Not too many ships have the scanners yet. I first saw the scanner on the Oasis of the Seas in 2010. Given the ship can hold 5400-6400 passengers it makes sense the scanner would be quicker and more efficient. Your assigned life boat location is related to the location of your cabin. The crew know how many cabins are assigned to that life boat. They have the list of how many passengers in each of those cabins. I suppose it's possible if 45 people were standing in front of life boat #10 and the roster shows there should be 45 people, then they wouldn't have to call out names.
You see this is a good question, I would like to know what the procedure is because no names are called out, no life vests are worn and no sea cards are scanned, then how in the world do they know if you attend or not?