I see no evidence that this merchant has 'cut him off'.
This page - http://www.computingfuture.co.uk/send-flowers.htm - frames the orignal site so if I click on the original site your affiliate ID doesn't get passed on. I would just create your own page with every link to the site being an affiliate link.
What was your conversion rate before? Have you tried contacting the merchant to see if there's any reason why your conversions are down?
Only start worrying if they don't answer your emails.