FormsCentral, itself, does not have a method of distributing forms, so it would not know about your distribution list. It's either an open online form, which can be gotten to by anyone with the URL, or it's a pdf, which could be distributed via e-mail or a web page download.
You can always track the completion of the form by looking in the form's collected data set. Then, you could work backward to contact those recipients who have not yet responded. But that means you need to keep track of where the form was sent, or at least know which people/companies were supposed to get the form.
I hope that helps,