Will a Buyer Be refunded in Clickbank even though the landing page doenst have a money back guarantee?
yes, they should. that's the condition of CB accepting a product. however, CB should never have "passed" a page that doesn't have such a guarantee.
Publishers don't have to put money-back guarantee on their websites. However, it increases the conversions, so most of the products have the picture of it. If the product is sold on Clickbank, then the customer can easily get a refund, because once their purchase a product, they receive a letter with receipt and all other information.
There's no requirement to include the guarantee on the salesletter. That's a marketing decision. The guarantee is automatically included on all CB products - the publisher has no say in if there's a guarantee or not - only on whether or not he wants to advertise that guarantee.