FWIW, I work for a large business to business computer reseller as a Sr. Buyer. We serve as the "vendor" and I buy from the "supplier". Now each manufacturer has their own slightly different return policy, some policies are even negotiated in a contract. Terms negotiated can include a percentage cap on returns per quarter, who pays for shipping (this could be either us or the manufacturer depending on the reason of the return), what is returnable and what is non returnable, etc. With all these differing variables never have I seen a manufacturer say "Mr. Vendor, we will make it up to you on your next order." The return is made, and no matter what the reason is, the supplier issues a credit to our account. Sometimes we pay the shipping, sometimes the manufacturer pays, but in all cases the financial side of things are kept as cleanly as possible by issuing a credit memo. Now I have no idea if these concepts still hold true for the e-cig industry, but that's how it works in the computer hardware industry and many others, from what I have gathered.
EDIT: If wrong product was shipped to us, you bet your ... we are making the supplier pay for the shipping back. This should hold true for any business relationship whether it be consumer/vendor, vendor/supplier, or consumer/supplier.