I suggested cookies purely on the basis that the only data that the poster stated they wanted to pass to the form, other than that on the page which went directly to the form, would the the referral source. Otherwise I agree that something else should be used for the circumstance you describe, but for simply noting the referral source of the site visitor I think a cookie is good enough for the minimal effort required (works for me anyway).

Having said that, Pagetta does not appear to have come back here for a couple of days anyway, so any answers may well be academic anyway ;)