I never thought I'd be saying this when I got up this morning, but at least for the most part, Chuckie boy is right. It would have been better if the employer had written the policy first, and I don't think there's any question that unemployment would be easier if the OP had waited to be fired. Nor do I think there's any question that confiscating anything but the phone is right out of line.
I still maintain that, while maybe a stupid policy (there are better ways to handle it even if this is an industry where cell phones can/should not be on the floor) the employer may require that the phones be held in the place of his choosing and that, while the employees who disagree with that place can/should leave the phone in their cars or at home, they do not have a right under the law to violate the policy if they opt not to (leave them home or in the car). I also maintain that, while I do not deny the possibility that in this case the employer may have crossed the line with the confiscation, if the OP got all his property back it's probably not worth trying to take any action about it.
Cell phones are a relatively recent invention. Employees for many years managed to keep track of their kids and get emergency messages by means of other methods. Those other methods all still exist.