Not able to detect referring url on redirection

Not able to detect referring url on redirection

I have a third party url like
http://affiliates.tyroodr.com/ad/175291/CD16284/&lnkurl=http%3A//www.flipkart.com/%3Faffid%3Dtyroo%26cmpid%3Daffiliate_promo_tyroo%3Faffid%3Dtyroo%26cmpid%3Daffiliate_promo_tyroo&subid1=168&subid2=f39ce6-c5c9-4280_770460
It gets redirected to site :
http://www.flipkart.com/?affid=tyroo
I have a button on my site. When a user clicks the button the a new tab is
opened and user lands on the later url by getting redirected from former
url.
Now while landing I check for document.referrer but it returns null.
shouldn't it return the former url.