True, but if Matt told a customer that it was his problem and not Ahlusion's and that he's on his own, that's bad form, IMO.
Matt should have told the customer about the tracking number, how to contact the USPS, and offer further assistance if necessary. I had a similar problem with another vendor's package and that vendor offered to contact the USPS also, and promised to resend the merchandise, free of charge, if our efforts with the USPS failed. Yes, that's above and beyond, but that's good customer service. Telling a customer that a missing package is "not our problem" is not good customer service.