We started branding our replacement heifers this year again too. It's the only identification, besides tattoos, permanent. Tags can be lost, cut off (illegal here if it's not your own cow), photo is a good idea, but I'm not sure how bomb proof it would be to show a picture of said cow and say, hey, that's my cow.
As per missing cows or not knowing they are missing.... if farmers here were to run to the police every time a animal is missing the cops would have to open a detachment just for that. Oh wait, there is the Brandinspector you can contact.
Nobody is going to help you find that animal though, that's on you.
It's easy here for a cow or calf or whatever to go missing. We are in bush country and the herds are usually not very close to home in the summer in larger areas. You can check every single day and still not see everybody, unless it's just 10 or 20 head sort of thing. Predators can snatch one if they really want and there is not much chance you'll find the carcass in bush country. Yes predators can be human too, most of the time you do find whatever is left of the animal though. That would be one instance to go to the copshop.
My point is, unless you are in open country, animals on small pasture and the herd is a smaller number, animals can go missing and you wouldn't know right away.
I haven't read the article, so I don't know what all the specifics are, but for the activist to hold the cows from the owner, that's just a stupid move. Yet, the world has gone so righteous and liberal, wanna bet the cops don't really want to get into an argument or confrontation with a tree hugger to confiscate the cows? =D
Anyway, just my 2 cents. Where is my coffee.