Wow. I'm sorry to hear about that. And I thought my job hunt was bad.
When they told me I couldn't talk to other co-workers in there, I would have told the plant manager to go "F" himself and stormed out. The company crossed the line there.
I can understand random drug/alcohol testing. I can understand going over the company policies on drugs and alcohol if there is an incident. But locking employees in the building, restricting them to certain rooms, and treating employees like criminals? That goes too far.
I don't think I would ever want to work for a company like that, and its a good thing I'm trying to start my own businesses so I don't have to put up with garbage like that.