You said you didn't like this, but according to your own rules the situation is already dead. I'd do a less harsh version of this or maybe even an "Oh, I thought you wanted to chat. Hope you're OK." It implies (I'm told) that the only reason you'd do something like this and not respond back is if something is wrong. After all, wouldn't a normal person respond? Is that not the standard?

I live a pretty busy, demanding life. I might want to talk the person I dropped a chat with, but sometimes I just don't have the emotional energy to say much and since I started it , I feel bad.