I had the same reaction to "stealing report" as soon as I read it. I mean, maybe it's not his area but these things have official names and a police officer is much more likely to use "industry jargon" than something your average citizen might come up with (which is more likely to be "theft report" IMO, but cops usually use a generic phrase like "incident report").

If an official report has been made, there will be a case number - I'd ask for that.

Secondly, what kind of weight would the box have with the contents removed? Australia Post aren't always as on the ball as you'd hope, but if a package has been tampered with in tranist and it's obvious in one way or another (damage to the outer packaging, unusually light or obviously empty parcel etc), they will usually reseal the package and include a letter about the incident, with advice on who to contact etc. 

You would be surprised the lengths people will go to for perceived believability and empathy. I had someone contact me claiming they never got the item. Before I could respond, they sent another message claiming they had received the package, but the contents had been stolen in transit, so I started asking some questions...

After my little round of questions, their story was that the package had been retreived by police (apparently the theif had a lot of stolen packages in their possession), but was empty, so it was handed off to Australia Post as it was no longer evidence in their investigation, and was then subsequently delivered by Australia Post, but included a letter from the police explaining the situation. I kept asking for the case number, in the end after repeated requests, they sent through a photo of a typed letter that (allegedly) corroborated their story. 

I wasn't done yet, though - I contacted the police and asked if it was a genuine letter; disappointingly they refused to confirm or deny "no comment, for privacy reasons" was basically their reply. However, i also contacted Australia Post, gave them the full details of what the buyer was claiming, and they were just immediately "yeah....absolutely nothing like that has happened". 

The kicker? The item value (including postage) was under $10 and it was sent untracked. 

Also had a few scammers tell me they were lawyers, or a justice of the peace, it's meant to be shorthand for "I'm a fine, upstanding pillar of the community, and / or law-abiding citizen, I wouldn't even dream of jaywalking", lol.

By all means work with them and I hope all of the suspicions here turn out to be off the mark, but just be wary of this one, and take as many measures as you can to dispute their claim if / when they try to make one.