"pigeon-hole"
Van? Well maybe but I have sneaky feeling that the company is just the MD and planting fake bombs doesn't need more than a car and a bag. I wonder if he has any offical authoristation, just imagine the reaction of the police if they had some reason to search his car and found a bag full of these things...
Quite or understand what "single point of failure" means, even people who should know better still manage to create (suposidly) robust systems with single point(s) of failure.
In this case with these things being laid in third party properties one would expect decent documentation signed off on installation and retrival. Documentation that included a description, or better picture, of the "device" and where it has been placed. Copies for the third party, the search company and file.