If your Mondeo has a CD player or aux button and it was recently touched, then your radio may be stuck in that mode. You can test this by attempting to connect another device, such as an iPod, to the car’s audio system. If it works, then there is likely an issue with the radio itself.
I would suspect a loose or damaged wire, with it working fine for a while once you plugged it back in. I would suggest taking the radio out, because as you said when the radio is off, there isn't a problem and see what functions you have and whether it plays up again. Mondeo Vignale estate in deep impact blue 2.0 petrol. Mondeo 2010 plate with 6000 CD: Bluetooth & AUX suddenly stopped working - Turned radio on and held power button in for about 8 to 10 secs and the the display went blank. Lifted finger off power button and display lit back up again. Both speedo cluster display and radio display should turn off completely and immediately and on unlocking both displays should turn on. Radio can then be turned on manually but note that with ignition turned off radio will display 1hr play time limit, after which it will turn off to save battery and extinguish all displays.