Technology

And those Hezbollah operatives can lose their pagers

And you can lose your car keys. But if someone asked you where they were, you wouldn't say "Oh, they're in a random place".

or they themselves can move randomly through populated areas with the hidden bomb strapped to their hip

The explosive charge was small enough to seriously harm only those who are in direct contact with it. There's a video of one charge going off in the middle of grocery shopping (speaking of your next point) with a person standing maybe 20 cm next to the explosion. That person was able to run away without apparent harm.

They never go to buy groceries, or stop at a hospital or school, or have their devices stolen or lost in some random location

There's no method of warfare that would never harm civilians.

a manner that has absolutely no mechanism by which to control where they actually are and who else is in proximity to them when detonated.

~~The pagers being bought by Hezbollah is the mechanism. Did you mean a real-time mechanism? Is this what it boils down to?~~ Edit: Sorry, I misread what you said. Changing my reply to: As you can see from the video, where they are and who is next to them isn't really a factor. I would agree that if they are in very close proximity to another person (hugging them of maybe riding in a crowded public transport), the explosion will probably harm the other person. Once again, relative to other methods aimed against targets operating among civilian population, this seems more selective, not less.