I submitted the disavow sheet on Thursday or so last week, and now we are complete gone for our main keyword.
From what I understand, the disavow tool would take weeks or, more likely, months to have ANY effect on your site either good OR bad - especially if the links were from low quality sites.
Yes, the disavow tool is "automatic" but it takes a long time for those disavowed links to be integrated back into the algorithim.
There IS the possibility that you disavowed a link that WAS giving you a lot of page rank, and that google crawls and indexes frequently, and that MIGHT hurt you quickly. But that would have to be from a site that google LOVES, like a MAJOR newspaper or something. It would have to be the type of site where they publish something and 15 minutes later it is indexed in google
have you double checked to make sure that you don't also have a manual penalty in addition to your Penguin hit.