Why would somebody's name suddenly disappear from my chat list on Facebook?

The person can choose to “go offline” on Facebook chat, which I believe would remove their name from the list.

What @Mariah said. They chose to be offline, but still are on facebook if they are replying to your messages.

@Mariah I will have to ask them if that’s the case, perhaps you’re right, and thank you……

I’m going to have to go off-line myself now so will attend to this again tomorrow, any other suggestions would be most welcome

Do you mean they no longer have a green dot beside their name? Or is their name completely gone from the chat list?

The former means that they have gone “offline” or invisible. The latter means that Facebook has randomly decided that the people who are currently on that list are people who you interact with more. Their algorithm for this doesn’t make a lot of sense, and a lot of people complain that the friends they chat with the most are missing from that list. There was a question about it here some time ago; I’ll see if I can dig it up. But if this is the issue, it’s not based on anything that you or your friend did intentionally.

Edit: Here it is.

@glacial: That was my question then, and to this day, and after seeing this question today, I still ask “Why is FB so confusing?”

You can choose to appear offline to specific people, even when you are actually online. Or, maybe this person chose to appear offline to everybody.

You can also choose to block chat completely – they may have done that

@glacial The name has disappeared altogether, there are only 2 people I sometimes chat with on Facebook and he is one of them.

Thanks for all your suggestions everybody and I will ask him if he has chosen to go off-line or block chat.