Not sure how it would make a difference.
When someone is abducted from anywhere but the inner core of a major metropolitan area, figure that the abductor has a vehicle, gets to the closest highway and is thereafter travelling at 55 or 65 mph. That averages out to a mile per minute.
For every minute, that means the abductor could be somewhere within a circle that has a diameter that is 2X the number of minutes. In the first minute, that means the abductor could be anywhere within 2 miles or 3.14 square miles. In the first five minutes, the abductor could be anywhere within a circle that is 10 miles in diameter. That works out to be 78 square miles.
In the first ten minutes, the abductor could be anywhere within a circle 20 miles in diameter and 314 square miles.
So, parent gets a text that Jr didn't get on the bus. Say one parent is still at home at the time. I doubt their first reaction is going to be to call the police. I think their first reaction will be to look out the front door to see if Jr missed the bus. Even if the bus stop is visible from the house, they're going to look for a few seconds to make sure Jr didn't get distracted by something (goofing off with a friend, a stray dog, a butterfly flapped its wings and the air current made Jr forget for a second why s/he is standing out in the great outdoors...).
That's 30 seconds gone.
Then the parent calls 911. Explaining to the emergency services dispatcher what has happened is going to take at least 30 seconds.
That's 1 minute gone.
Assuming dispatch correctly perceives this as an abduction vs Jr forgot to swipe his/her card or the automated system made an error, they are going to dispatch a patrol car to Jr's house. Let's say that this is the one day of the century that there is a patrol car within 30 seconds of the house.
That's 1.5 minutes gone.
Officer arrives, starts to interview frantic parent. Parent has to explain again what is going on and provide a clear description of Jr. Let's say this is the calmest parent ever and the best police officer on the face of the earth and all this takes only 30 seconds.
That's 2 minutes gone.
By now, Jr is anywhere within a circle that is 4 miles in diameter and 12.5 square miles in area.
Sure, the police may be able to throw up roadblocks along major thoroughfares but their chances of stopping the abductor are constantly going down.
Plus, the police know that 999,999 times out of 1,000,000 Jr wasn't abducted. Jr got distracted, Jr thought the bus had already come and has taken off on foot chasing it, Jr and his/her best friend were absorbed in a Twitter flamewar and forgot to get on the bus, the automated system misfired, etc.
The chances of getting the perfect, instantaneous police response each time that card is not swiped goes down with every false alarm.
And then there's this: the chances of being killed by lightning each year are roughly half the chances of a child being abducted and disappearing for good.
When I find myself thinking "this or that should be done to prevent a child from being abducted" I ask myself if I think that much effort should be put into protection from lightning strikes to give myself a risk assessment check.
If I wouldn't do it to protect from something that is twice as likely to happen as a child abduction, that's a pretty good indication that the proposal doesn't meet my personal benefit to risk analysis.
Other people probably feel differently and that's fine, too.
