Well by all accounts (of people that seem competent on the internet...) the source is just fine as it's own beacon. Even detectable by a low flying helicopter with the right equipment.

Well, by the account of the article you are responding to the source has been lost.

Not very useful beacon if you don't detect when you lost it or you need to put an enormous search party to find it.

We have GPS devices with satellite comms that can periodically transmit information about where they are that anybody who plans to trek in the wilderness can buy and use to start a SAR operation.

Why not just put it in a bulky plastic blister pack, like we do for like, razors? Make the tiny thing larger and harder to lose?

But it already was larger; It was part of a “density gauge” (https://en.wikipedia.org/wiki/Nuclear_densitometry). It’s not as if somebody but this in a trouser pocket (would be extremely foolish, of course) or laid it on the car’s dashboard (slightly less foolish, but still extremely so) and then lost it.

I wouldn’t know whether the pictures on that Wikipedia page resemble what this was on, but I expect it to have been of similar size.

The problem was that something (¿excessive car vibrations?, ¿a speed bump?, ¿bad packaging? ¿bad design of the gauge? That’s to be researched) dislodged it from that device and that it then dropped out of the car.

Now I wonder why wasn't it glued, packed or something in larger material. I think there should be something light and relatively non-opaque for radiation.

I haven’t read any indication that safety rules weren’t followed, so presumably because whatever it was packed in was deemed safe enough.