For those speculating as to where some of our cards might have been over that past few months this site I found on Reddit is by a guy who has included Air Tags in a number of packages posted in England over the past few months for various International destinations.
It’s quite fascinating…
I’m afraid i had to Google what an air tag was 
It would be great to see exactly where our postcards are, i think this is an expensive way of doing it though 
Oh, this is cool! 
It reminds me of that one time someone put a camera inside a parcel, so that they could see how it went through the mail:
I remember watching a video which proved that the postal service from the UK to North Korea was suspended with an air tag. You do wonder with remote destinations how often they can check a route is still working!
^ The video if anyone is interested: it is rather long! The part about Royal Mail starts around the 24 minute mark.
These are super interesting indeed!! Thanks for sharing this like.
I had seen this video back when it came out also! …and was also the first thing I thought of when I saw this thread. 
Love stuff like this.