Had that happened they would be dramatic, but who is to know what really happened. I mean it's much easier to assume what the other person did or said or not do, their motives, actions, words, lack of..
Did they leave you hanging in a live chat? I am sorry, if that is what happened. Because many times I write to people, and if they aren't around.. they may not read what I wrote.
Try and give them a day to reply. Maybe they had a medical emergency, or something like that. Shit happens to all of us.