wrong title

I think I see now what's going on.

Here is a quick "what I'm trying to do": I have thousands of business nodes and each of them loads the same webform. I have 2 custom hidden fields in the webform: emailto and referring_url.
- emailto - the email from the business profile which is being pre-set from the business node when the form is rendering. It holds the email value for the conditional email, as so the actual business receives.
- referring_url => http://'.$_SERVER['SERVER_NAME'].request_uri() - the url of the business node where the form was filled out.

Everything works just fine as long as you don't miss any required field. If you miss a required field - it redirects you to the actual webform node where I'm automatically loosing referring_url value. But the most weird part to me is that I still see all the values in the fields, even the hidden ones that were pre-set on the previous page (the business node), but on submit - the value of the hidden emailto is empty. I can see the value entered in the HTML source code... As I said it all works fine if all required fields are entered, but it loses some hidden values after the redirect to the webform node if required fields were missed.

Any ideas on what might be causing this?

Thank you.