If you bought it off a dealer, take it back and tell them you want the code, as he should not have sold you the car without it's radio code.
I once did, by telling them that if I had the need to disconnect the battery I would need the code or the radio would be useless, and although they tried to get away by saying it would cost me, I was forceful and in the end they provided me with it for free.
Try pulling the radio out of the dashboard slightly, sometimes the codes are written in felt tip pen on the casing. My 2 most recent cars luckily proved this!
You've nothing to lose by doing a quick check!