Deleted Presets

Well firstly let me thank you for saying initially that you're using Windows - I wish everybody would state the OS they're using, because it can often make a big difference to the response they get.

It's not so easy to re-establish a single preset, but it's not difficult to restore the lot. It's only a problem if you've stored any of your own as well, because they are going to get lost if you do this. Anyway, go to C:\Users\{username}\AppData\Roaming\Adobe\Audition\13.0 and locate the file called EffectPresets.xml. Delete it. When Audition restarts, the original file will be re-instated.