So this is where CBT helps amongst other things. And perhaps it's easier to do it on here rather than putting it into practice yourself.

You sent an email to an organization which is running a conference and you haven't heard back. You think that your email is being ignored because you misunderstood the directions and/or you think your request was presumptuous. Either way, you think that you did something to cause the radio silence.

But, perhaps the person who received the email didn't see your email amongst all the other emails he or she received because the conference is only a few days away. If this is a conference, there are actually probably only a few people who are doing most of the organizing and maybe this is all volunteer time for them as well. Therefore, maybe the email was overlooked. Maybe that person just didn't get back to you because they feel overwhelmed, but I am almost positive it has nothing to do with the content of your email or when it was sent.

So training yourself to "re-tell the story" in your head is a good way to help stop the ruminating.