Yet another sign of the times, when you can't even buy a Lego set without wondering if you got what you paid for.
Don't get me wrong I've noticed in the last few years or so, things like this has been happening, but what can you do.
I've seen ruddy great holes in the boxes to glued up sides, (these are harder to spot) in fact almost impossible, but a while back there was a solution, and it came from a drug company?
Now I don't know if it will add to the cost of Lego or not, packaging is a funny thing but here goes, it had all to do with the way it's sealed.
Inside the box you have the sealed bags with instructions right, outer cardboard box is tightly sealed with glue at both end (what's the difference?) None! It's next bit that's interesting, security seal tape around both ends with the words if broken no refund. We're talking pretty strong tape here that once peeled with take the box cover with it!
Finally a plastic strap sealed around the both ends, this applies to the big more expensive sets whereas the smaller sets can be seal wrapped in clear plastic, again with the security tape on both ends.
It won't fool proof it but it will make it much harder to return the item which is how they get away with it.
Another idea is to put the actual weight on each box so if the box does come back it has to be weighed, over or under it can spotted.
If I seem a little paranoid so what, there's nothing worse than building a set and finding some bugger has made off with a prized mini figure, I know, my star destroyer was missing Darth, okay so he was easy to replace, but why should I?
Then there's the problem of convincing Lego, after all they need answers too, before they'll give you a replacement.
My final advice is look! Check very carefully before you buy, check all round the box for signs of tampering, it's not fool-proof but it helps.