Most carriers will cock it up at one time or another, but you would at least expect an adequate explanation rather than buck-passing.
Royal Mail have managed to take 3 weeks for a parcel we've been waiting for, and still no sign. Spoke to a guy I know at the depot and lo and behold, if a parcel is returned there it sits in a pile, then more arrive, burying the earleir returns, and so it continues until they clear the 'recent' backlog and find your item!?!?!? First in, last out....sucks....
I sent an item recorded delivery at the beginning of October, the recipient wasn't at home and didn't go to collect it(another story), Royal Mail have now managed to lose it completely dispite an online enquiry/complaint. Their response....Ooops, sorry!