How is this Royal Mails problem or fault?
Is an interesting thread so I thought I'd throw in my tuppenth worth.
If it's an e-bay purchase there is nothing stopping someone physically sending an empty box. You're not necessarily going to check it on collection in view of the delivery person so you're pretty much stuck with your word against the post office & the seller that it was actually in the box & that it was sealed at the time of receipt. Any of the 3 (including the recipient) could technically be responsible for the alleged theft or deception.
There are nasty people who work at the post office. My eldest had a bank card stolen & as I live near a sorting office it doesn't surprise me that crime goes on there; there are usually at least 1 or 2 police cars parked in their car park every day.
The rules for receiving something by post are simple:
1: ALWAYS CHECK THE PACKAGING!
2: If the packaging looks tampered with either refuse to accept (if you have to sign), or draw the post worker's attention to it & open it in their presence. If it does not contain your item you have solid proof you have not received it.
3: As soon as possible contact: the police; your credit card company; the carriers; the place of purchase (but not the seller unless they meet the criteria in 4).
4: If you have good reason to contact the seller (as in they are a reputable company) then do so...otherwise assume they are responsible & have set up a single-drop account for your money & refuse any form of contact as it is a police matter.
On the plus side, a phone has a unique IMEI number that should be traceable by the seller through their line of purchase if they didn't note it. That would help separate any innocents from suspicion.
You need a police incident number before you can do anything else (in the UK), so they should always be your first call.