Why has one of my two propane fireplaces suddenly gone completely out?

Before I speak to the problem of the one fireplace not working let me say a couple of things. First, these types of appliances; gas logs in open masonry fire places are some of the least efficient ways to heat a room. The vast majority of what little heat they make goes up the chimney. In a given 24-hour period you could experience a net loss in heat to the space. Second, those units should not be used without their logs in place. The logs are an integral of the appliance and its safe burning. They are an approved appliance if they are used according to manufacturer's instructions. With out the logs, they are not an approved appliance. As to the malfunction in the bedroom unit, it is probably something simple to repair. And those units have layers of built-in safety. No cause for alarm. Simply because it is not burning is no indication that it represents a hazard. Without a standing pilot all the valves close to stop any flow of gas. You may just need to relight the pilot, after you get the logs set properly.