Why would my radio and A/C heater just go out without blowing any fuses on my Lexus es300 1994?

Fuses only blow when something is shorted to ground as in a wire rubbed through or two wires overheated and melted together. Things will turn off when there's an intermittent break in the circuit, just like when you turn off the ignition switch. A fuse can have a poor connection, a connector terminal could be spread or be corroded. A ground wire could be loose or rusted by its bolt. The best clue you have is when two totally separate things act up at exactly the same time. You need to look at whatever they have in common. That can include one section of the ignition switch. Also, since they're both in the same area, they might share a ground connection on the body. Look for anything else that stops working at the same time such as power windows, cigarette lighter, interior lamps, and things like that.