Why does the author find this so difficult to understand? I read the error and both immediately know what the problem is, and can guess a likely series of event

Why does the author find this so difficult to understand? I read the error and both immediately know what the problem is, and can guess a likely series of events that caused it. 1. You load a page with the message, and your client (browser) renders its contents after fetching it from the server with an API call 2. Some unrelated process causes the message to be deleted on the server 3. Some asynchronous process on the client (like a periodic refresh) tries to get the message, but it's since been deleted, but the client-side rendered state stays the same 4. Thus the error: the message doesn't exist anymore, so you can discard it to manually make your browser state consistent with the server. Or you can just refresh and it'll be gone. So if you want to save the contents, copy it in your clipboard first, before refreshing.