Phone ****** from package sent

Last week Friday I sent my sister the phone I was using before upgrading through the post office, the box was properly wrapped and sellotaped and placed in the post office courier bag to avoid damage during packing and transportation along with the rest of the posts from the post office, the person on the other end received the box with just the spare case for the phone and a charger, the cellphone was gone and the box was no longer wrapped and sellotaped like I had done, when I went to the doornfontein post office to inquire about the the manager had no idea as to what happened to the device and said he could not do anything about the issue, only the receiving end should do an investigation. The guys from cape town took my sisters details and said they would get back to her no later than today, the person who helped her like the ones from my side showed no interest or hope as to whether the phone would be recovered. The reason I am sending this now is because the issue has been eating me up and instead of doing my work I can't think of anything besides this, the phone is a samsung galaxy s5, I payed close to R10 000 for it through Telkom. Please help me.