Recall that the Ptolemaic Kingdom was created out of the break-up of the Alexander the Great's empire. The Wikipedia article gives 320BC to 30BC. Its leaders were Macedonian Greeks. The Greeks had trading cities along the Italian Peninsula as far back as the 600 BC era, in part to trade with the Etruscans. It's not that difficult to conceive of this cloth(250BC,) being included in some trade shipment that ended up in Alexandria and then carried up the Nile to Thebes.