No, there's no way for vendors to "ban" buyers in that way. GMemphis is/was a scammer (aka CanadianLTD, mtljohn, etc.) so yeah, he was banned. With the other vendor, it could be that they are no longer a vendor, or maybe they are in vacation/stealth mode. Not sure, but I *am* sure that the only way vendors have of "banning" a buyer is to cancel their order.