I had an example were a courier claimed to have delivered. The signature was a flat line. The receiver was adamant they had not received anything. We kicked up a stink and 24 hours later the courier arrived at their house with the parcel but did not ask for a signature. The online system still showed the original delivery data. Another time I tracked a parcel sent for me which online claimed I had received it…(nope)… turned out they had delivered to the right house number at the wrong street and the idiots there signed for so online all looked ok. I know some companies are using trackers now plus making the driver take a photo to catch this. The systems are not full proof, stay strong, don’t panic and gather all the info you can. If necessary, report it to the police. As others have said I feel sick for you / awful situation and I wish you luck for getting it back.