LOL its probably because Macys is so cheap, most of their door sensor detectors don't work! People do grab and runs all the time at my ghetto macys, and the only way we notice is if we see them running outside with an armful of clothes. We asked the security guys why they don't just fix the door sensor things, and they told us that the amount of money it would cost to fix it was more than the amount of money they loose in theft each year! Which I think is stupid, because that amount of theft adds up year after year. Macys is such a cheap company, they refuse to even fix our stupid A/C unit even though it breaks down monthly...
Anyway, my point is at least at my store, they're so used to people accidently going home with sensors (since the door alarm doesn't go off to catch them) that they probably automatically just take them off. Which is stupid because you are supposed to check the receipt...